i´ve got a problem when i try to change the cost of the orbital weapons.
i changed the cost x10 (80000/6000/5000). but when i start a new game against the ai, they dont build any constructions (eg mines on the asteroids). they only build ships.
The AI keeps track of what it wants to build using 6 "build lists": one for ships, one for research labs, one for techs, one for non-labs logistics structures, one for tactical structures, and one for planet upgrades (eg. explore planet, expand logistics slots, etc.). Each list is ordered by priority, and the AI will save up its resources to try and buy the item with the highest priority on each list. Though the priorities are recalculated each "AI tick" (about once every 10 seconds), certain items have hardcoded priority and will always occupy the topmost spot in their list: for example, capital ships have hardcoded priority over other ships, while capital ship factories have hardcoded priority over all other logistics buildings. Thankfully, almost all items with hardcoded priority are only added to build lists if all research prerequisites are met (the only exception I know of is the capital ship factory).
It sounds to me like you've got something with hardcoded priority blocking up the build slot for non-labs logistics structures, since that's the list for things like extractors, frigate factories, trade depots, etc. I highly doubt it's to do with your Orbital Weapon code, seeing as 1) the structure still requires research prerequisites, and 2) to my knowledge, orbital weapons use the tactical structure build list, not the non-labs logistics one. To troubleshoot the issue, turn on the AI for your current player in your debug game, then turn on the "build list" overlay via Dev Menu > [d] Player Info > [f] Show Build Lists and see if anything's blocking the relevant build list.
As GoaFan said, the game's AI is still quite a murky subject. However, I did spend a good amount of time writing up all I could find out in my Artificial Unintelligence thread; the thread is also linked to in this thread's main post, but it's under "Third Party Tools", so it's understandable that you couldn't find it.