How Far Down the Rabbit Hole Would You Like to Go?

That is what is what I am currently asking myself. How far do I go with the MR-S. How much money do I sink into it before it is too much. A used Lotus Elise is a mid-20k car now. If I dump too much money into the Toyota I may as well have bought the better looking, better suspension equiped, lighter, 2zz powered (same engine) Lotus. I won't be too far off after building the 2zz and getting a hardtop...

Why do I waste money?