They're never worth it early on. And that includes Sova rushing, however if the bug is fixed, paying to upgrade the Sova early could be the lone exception.

My take? The first cap is left to develop on its own. The only time I ever bother with buying levels is when I'm nursing a second cap to a higher level. If it is over half way there, and won't see battle soon, I spend the money to get the upgrade. The problem with spare caps isn't so much getting the experience because the odds are you and your opponents have fleets that are ready to knock the snot out of feach other.  The problem is keeping them around to get the experience. It's too easy to micro away an upgraded cap, let alone an unupgraded one. 

Hence why I nurse them along and buy about 250 exp of the 500 the cap has by level 5. (I just don't see the point in buying the upgrade slot upgrade, if it opened up level 5, sure, but spend money so i can spend more money on level 4 caps? No thank you. I'll go find some pirates for free).

Mass Tanscendance is that nail in the coffin Advent uses once you have 6+ caps, a monster fleet, a decent eco, but your opponent is starting to utweight you with eco, so you HAVE to beat him with a fleet that is stronger pound for pound. It's just too expensive to justify buying it unless you have 6+, preferably 8+ caps. Synergize your cap abilities like mad and watch the mayhem ensue.

For me purchasing Cap levels is a must. by first contact i want my cap on its way to level 5 not level 3. for 2750 1250 for first level and 1500 for the second its a steal. You have to remember with every level shield armor hull and weapons increase.  I would also say a level 5 marza is much more of a threat then a level 3 if Marzas your preference.

Anyway, Just my two cents

-If not then finishing levels as the last poster said is a good idea

At 10.0 credits/sec starting income, it would take 275 seconds (or 4 minutes 35 seconds) to recoup the cost of the first two purchased levels. The calculations in the OP also do not take into account lab costs, logistical slot upgrade costs, or planet colonization and upgrade costs, making the level 3 to 4 upgrade more costly than what is shown.

Some excellent replies.  I too, wonder if you should be able to buy Level 5 reseach (after a second level of research on the existing techs.  For tier 3 Vasari research it would cost $1100, 175M, 275C; or $100 more, and 25 M&C more than the existing costs, for each race).

But this all depends on the presumption that you'll buy multiple Cap Ships.  I just can't justify that very often, considering how costly additional Cap ships are.  Just how expensive?  Rough calcs @4, Cap Ship cost: $5600 ($3000, 400M, 250C).  Then there is the fleet research required for additional Cap ships:

Cap#        Research  Total$   Total spread across

First            Free         -0-
Second       1500       7100
Third          2800       8400
Fourth        3800       9400
5 and 6      3400       9000             7300
7 and 8      4150       9750             7675
9 and 10    4900      10500             8050
11 to 13     4700      10300             7166
14 to 16     5400      11000             7400

The 14th Cap ship will cost almost double the first replacement, or $11,000 (vs $5,600).  Not including additional fleet slot cost, or Lab costs. 

Or the fact that you'll probably have to rebuild your Cap Ship Factory that you scuttled at the beginning of the game.  This will cost an additional $2400 ($1000, 250M, 100C).  But at least this cost can be spread accoss several ships if you build more than 1 more.

I think N3rull made a good suggestion at the Making Cap abilities viable thread (reply 147):

[quote who="N3rull" reply="147" id="2361176"]

"I think a player could start with 2 capital ship crews available.

Fist cap should be free, as it is.
Second should require construction costs only.
Third should require additional research.

That way building a second cap is not excessively expensive, and would encourage doing it if someone is not doing econ...

I also think all races should have means of constructing higher level caps in later game."

Edit:  I noted an error in my calculations, and edited the table accordingly.  The research for the fifth Cap ship opens up 2 Cap ship crews.  So if you build a sixth, that $3400 research cost can be spread across 2 ships, so half the cost then (1700+5600=7300).  The 11th & 14th reseach open up 3 crews, so 1/3 the cost, if shared.  The 14th ship will still cost $11,000 until you build the 15th or 16th. 

The fifth & sixth Caps ships are much better deal than the fourth ($7300 vs $9400)!

This is why when you think you'll get a second capital ship early on you don't scuttle the factory.  Seriously, unless you need the logistics slot it's not that big a deal.  You get about one extra frigate with the money you earn, and you've thrown away the opportunity for a fast second cap.  It's worth leaving the structure intact to maintain the strategic opportunity IMO.  It's a tall investment, but successfully pulling off a fast second cap is a great way to procure a long-term advantage. 

I personally don't think we should start with crew for two capital ships.  This would make two-cap starts way too powerful on large-fleet settings (it's already a great opener there; if you didn't have to fork out crew research it'd be taken for granted).  Although the total expense is a bit of a problem, I think the crew research has an important role in controlling the availability of capital ships.  I think it's actually a good mechanic to have a high initial investment to access the capital ship, but then waiving this cost if you have to replace it.  Take away that crew research and I think the relative penalty of losing a capital ship increases substantially.

I'd rather see a nerf to LRF and bomber damage vs capital ships to make them a little tougher (and therefor worthy of the investment) than any cost decrease to crew upgrades or the like.

I personally don't think level 5 should be capable of being bought.  This reduces the chances of encountering a level 6 capital ship by complete surprise.  That said, I do agree all factions should have a cheap way to access level 4.  Advent, once the research is done, get it for free.  Vasari and TEC need something as well.

If you are rushing, or being rushed, scuttling the factory is almost a must.  The second cap ship is such a tall investment that it can't be done too early, without seriously stressing other needs.  So in the meanwhile, you've got a big wasted investment, taking up valuable (& needed) logistics slots.

Most people I see, scuttle their Cap ship factory.  And if they rebuild one, its much later, and much closer to the front lines.

Bumping this post, because of other discussion about buffing Battleships & Support Caps. 

It is interesting how online strategy has evolved, from single cap starts to dual cap starts, (and then scuttle the cap ship factory).  The 1.18 patch buffs to Carrier Caps, (and the need to counter buffed LFs with Scout rushs), made it so that it is worthwhile getting a second cap.  Dual caps makes it harder to level them up because experience is being spread across two rather than one.

I still think an increase in the amount of levels we can purchase would be beneficial.