it feels like the later levels should be WAAAAY more expensive, the initial wall/gate unlock are fine, but the upgrades should be as followed imo:
up1: 2pots of red/green/military 400 times
up2: 3pots of red/green/military 500 times ( 750 hp walls for 3 first sciences is already very strong in comparison to 350 base, add to this free autorepair)
up3: 3pots of red/green/military/blue 500 times (again 250 health and 5 hp is a lot)
up4: 3pots of red/green/military/blue/purple 500 times
also if you think its good a good idea, you could add infinite science, at a + 200 health and +5 health/sec recovery per infinite level, costing 1 of each per 60 sec, 500 the first level increasing by 500 per level.
