Most vette parts ARE cheap!!!
Try buying old mopar parts...wow....
Some vette parts are absurd...try a fan shroud for a '75! (I made one out of lexan rather than pay that much...)
But body panels, suspension parts, drivetrain parts....wow...cheapest thing out there for vintage cars. Not only that but most of them are higher power or other performance options. While the recovered seats are high, for example, you can buy every single body panel for only about twice that! A simple DOOR for a Mach 1 mustang can easily go for a grand. The body parts are so cheap it's usually worth just replacing them after significant damage rather than repairing them.
The paint costs are also due to the high expectation levels of the standard vette enthusiast, who often don't blink at $5-10K for paint. The same under $500 "good enough for a few years" MAACO type job can be had for vettes just like most mid twenties street performance people have always gone for. $2500-3500 can buy you something a lot better than ever left the factory.
As far as this performance thing for C4's...PLEASE!!! They DO handle great, but with the right upgrades, the C3s are as good and the earlier ones don't have the same weakened aluminum rear end section that is shared in weakness by the C4s.
As for the REAL performance aspect - POWER! - only the latest versions of the highest end C5's and soon to come C6 Z06 even get into the same league as the early C3 bigblocks, even factoring in the most efficient drivetrains. Putting one of those big blocks or an even more common more powerful newer stroker big block into any what, pre-79 (or is it pre-77?) C3 is as easy as any other engine swap, except for a change to the steering linkage and I believe PS mounts.
Aside from worrying about the always weak factory Dana 44 and even 36 center sections (which are still stronger than the aluminum versions), a C3 can easily have a 600hp medium big block dropped in it and run fine unless you do constant heavy launches. 600hp engines push C4 (and even C5&C6) frames and drivetrains to the breaking point at even very conservative uses.
Look at the condition of most exotics like Callaways and even ZR1's that were actually driven. It's common knowledge at vette shops these "higher powered" specialties - which at best reach 65-70% the power of a decent big block - end up needing enormous work quickly as every part has been pushed to the near design limits of the C4 platform, unless they were rarely or sparingly used. On the other hand a higher powered - and much higher torqued - big block C3 is not generally in much more "ragged out" shaped than a 75-77 small block with the weakest engines ever put in vettes.
For even midpowered applications, all of them need the strongest half shafts and especially outter and inner axle stubs as well as the center section, but these are of a common concern on all IRS vettes and don't favor one generation over another.
I do think the best bang for the buck on an all around sportscar is a nice mid year C4 ragtop, but god help you when you even want to change a distributor "cap" and wires.... I was stunned when I recently saw this. A leaking valve cover gasket is an undertaking worse than pulling the heads on an earlier small block. At $7-10K for a really nice one, the car handles like a dream and has at least decent power, but modifications are far more difficult and expensive, with many fewer options.
Likewise it is hard to beat the "bang for the buck" of a $20-25K 3-4 year old C5 with it's exquisite handling and more than acceptable factory power levels.
For all around street and highway performance and simple power though, the C3 is the best choice - especially for the modification purposes of a home garage car builder that 15-20 years ago, at the end of the terrible "crappy Detroit product era", would have gone for a '70 Camaro or a hemi Cuda.