I am trying to decide whether to keep my 04 Audi TT or get a new car. It needs a new transmission which will cost anywhere from $4-7000 ($7000 from the dealer, but no one else in town is willing to touch it because it’s too “complicated”). I looked up the KBB value and it is worth about $8k with a working transmission and $7500 with a transmission that needs to be replaced. How is this possible? Am I missing something? And that’s the trade-in value, the private seller value doesn’t even change. If anyone knows why this is, please tell! Also, advice on buying new vs. maintaining is appreciated - but only specifically if you know about what more expensive repairs will be coming up for the Audi TT (85,000 miles on it now). I have already spent $3500 on it in the last year, and might be adding $7 grand to it now for the transmission…
I will miss it if I have to replace it with a 2010 toyota though 
Either you found the wrong number or the book you used is wrong, as you suspect. Typically the value with something wrong is discounted by the repair cost, often more.
You’re in a tough spot, relatively new car with major repair. I wouldn’t spend $7k on it, I might $4k, but that’s still a lot.
I played with the “new” valuing system KBB has and am very skeptical. The issue is that it places a single value reduction for the transmission repair or replace question,and in your case assumes a very optimistic, unwarranted outcome. It doesn’t ask for details or explanation of the real replace/repair requirement. There is a whole lot of difference between a minor repair and a required $4-7K replacement, and KBB is not accounting for that distinction in their computations.
Where are you located? Sounds like an easy enough fix to me…
Find someone willing to give you $7500. with the bad transmission then put the money on a car that’s in good working order. LOL Sounds like the KBB valuing system has some serious flaws.