I've also considered ditching the gti in favor of a proper track car several times. There's really not much out there that doesn't cost an arm and a leg to drive on track. The gt350 and zl1 are decent cars, but I can come close to touching their times in the gti and they would run me at least 15k$/season compared to the gti's 6-7k. You also have far fewer options in tire choice and brake choice. Just make sure you don't get carbon ceramic brakes or you'll be paying 15k/yr for brakes alone.
Much better options would be a cayman, a boxster, Elise, exige (whoever said they understeer just doesn't know how to drive them... Just like every mid or rear engine car you HAVE to trail brake to get that weight to transfer forward for rotation. Coming from an mqb car is a good learning step), an old miata, spec e30, spec e36, spec miata, spec boxster, or a spec z.
I generally go through 2-3 sets of tires and 3 sets of brake pads/rotors per year. Add to that the fluids, other faster maintenance items and things that break, and the gti pushes the 6-7k/yr mark quickly. Real costs per weekend are typically 1.3k. A miata is 30% cheaper, a spec boxster 75-100% more, and something like a grandsport corvette (only one worth owning for a track car right now) will be 200% more.