Interesting and you'right about costs when refurbishing a TT 993 with 144k km.
Sounds like it would be a deal for someone who has the know-how, time and facility to DIY.
Still, without a credible written leak-down test, hard to say. I consider leak-down far more important than a compression test.
If the body, paint and interior is good, the rest is mechanical and a matter of parts and labor and like you said, do the math.
And yes, the fees and taxes, sigh.......