As an example:
For my car (which includes mods from the previous owner and my own mods) to give "just power":
* HKS Pod Filter = ~$300
* Boost Controller = ~$300
* FMIC = $1800
* Full exhaust = $2000
* 520hp fuel pump = ~$340
= ~$4,740
But then to put that power to the ground and to stop (obviously not -required- but deffinetly wanted):
* Michelin Tyres = ~$1000
* Suspension = ~$2,700
* Brake Upgrade = ~$2000
= ~$5,700
Now theirs $10,440 and you havent even done other "general" things like ECU, Turbo, Injectors so for the people suggesting Turbo upgrades i'd like to see you bolt on a turbo for under $5k and see how long it lasts (but thats just my opinion).
PS, the above gave me over 200rwkw too so im quite happy with that.