I assume this is the same JJJames with the nice Dakar euro spec M3? You can't have that and an Alpina
I mostly agree with what LordVader is saying, although that particular B6 probably isn't a good indicator of Alpina values overall. At least to me it wasn't the most desirable model. The B6 2.8 was a bit of a lower spec model to start with. And it was also Auto (but not switchtronic), regular seats, no digital gauges, etc. It did sell about a week ago, but no idea for how much.
One other thing I'd caution you about if you're thinking about picking up an Alpina is insurance. I had trouble getting insurance on mine here in Ontario, ended up with specialty insurance through Hagerty which isn't a viable option if you want to daily the car.