I need to know im still a noob but with lots of ctp and want to know a price 1 of you guys would of paid to max out a vm rich gas planet to a colossal 17x mega rich plasma

It's usually around 2.5k

As several shops currently are offering them at 2k, I would have to disagree...rule of thumb: shops are almost always at the top-end of the price range. 2k or less.

Shop?

Depends on whether you want to wait and if you need it to be a plasma. VM 15x Rich gases are 1.8 ctp i think, the Colossal Plasmas at 17x are around 2.2 now i think. This is better asked in trading post i think, Most traders just go there.