I spent nearly 10 grand boosting my SI. I know all about purchasing quality parts
In fact, the kit itself for my car cost more than what I'm seeing for TT/SC kits for this car, but I'm sure there are other parts besides the kits needed whereas my kit was 100% inclusive of everything needed. If a TT or SC for this car costs 10-12k, I would be ok with that. Much more than that and I would question my sanity. For my specific car, you would never see 500 whp for 5k unless you bought really crappy parts, or bought them used.