Lots of things go into "value" and price. Rarity, condition, popularity, usefulness and available alternatives all weigh heavily. Sometimes price makes sense. Sometimes it doesn't. Sometimes it's just the right item at the wrong time.

Yes, the BSA is a machine made gun. But it is a true British/Birmingham gun. They only made about 40,000 guns and the vast majority were plain workingman grade guns. Very few had any embellishment at all. This one was clearly not a run of the mill gun from the BSA factory. There may not be much collector interest but it is certainly unique.

Anyway, here's a few pictures: