would be a good alternative to an S4 Avant that the USA won't get. Dressed about the same way, what would be the projected costs for an S4 vs. the B8 Avant 3.0 TDI?

It'll be as fun (or more) in the oomph department, but it won't handle nearly as well.

3.0 tdi 220 kg or 485 lbs

3.2 FSI 171 kg or 377 lbs

BMW

3.0 tt 190 kg-195 kg depending on source or 419 lbs - 430 lbs

3.0d 222 kg - 214 kg depending on source or 489 lbs - 472 lbs