$100 does seem high. However, I broke down and purchased one for myself (note, in my experience I maybe shoulda checked with the wife BEFORE ordering, but better to ask forgiveness than permission).

With the part in hand, you can really appreciate the size of the original stock, and a LOT of machining (due both to the amount of material it looks like has to be removed, as well as the detail/precision fitting). TBH, I am shocked they can produce them for $100 without selling a BUNCH to make up for the initial setup and programming (in addition to the ongoing tools/materials costs).

If it is cost effective for you to make one for yourself, you are definitely one of the very few. That being said, if you proceed, I hope it turns out great. There is something about putting that chassis in that looks sharp and feels nice (in hand and on the track).