Well, that's rather subjective.
Shopping wisely, I figure parts at $5k and a local shop that works for $85/hr. Call it $6k. I bought a ten year old car for less than half of what it sold for new, and I'd guess the premium Porsche charged for the S over the base was $8-10K.
https://www.youtube.com/watch?v=WN_h9juITLk
I posted this link elsewhere and never got a response. Fabspeed has a good reputation as far as I can tell, so why lie about your numbers? Is there any good reason why I shouldn't trust them? Also, they don't upgrade the plenum and throttle body in their runs.
Looking at your signature, I'm guessing what I'm looking to spend one time on upgrades is pretty close to what you spend a year insuring six cars in southern California.