28-33K IMO.
There's one on BaT right now that's very similar - same model year, same color combo, almost identical mileage. Biggest difference is the BaT car is DCT, and also no records of TA's or RB's.
Check back in 3 days when the auction ends, that'll give you a ballpark estimate. Then add several thousand more for the one you're looking at, being it's a 6MT and has TA's/RB's done.
Note this same BaT car sold on BaT last summer for $30K, but the market has cooled quite a bit on these cars.
https://bringatrailer.com/listing/2009-bmw-m3-sedan-8/