The Prism is a building added in v1.041. It is currently the most expensive building in the game. It has a base price of 75 billion (75,000,000,000) cookies, and its max CPS is 352,000,000 when fully upgraded. It currently has five upgrades, the most expensive of which costs 600 quintillion cookies. At 15 Prisms, you unlock the rainbow Grandma upgrade, which makes Grandmas twice as efficient.
The cost of buying 100 prisms is just over 587.1 quadrillion cookies. This jumps to 636.2 quintillion for 150 of them. To reach 200 of them, you need a massive 689.5 sextillion cookies. The most Prisms you can have (without cheating) is 4901, after which the price gets too high for the computer to process, and it says "Infinite". Even if you have infinity cookies (also caused by having too many cookies for the computer to process), you will still not be able to buy it (unless you cheat).