I think that there must be many more than 1bn though? The area of the disk is roughly 3.14^10 light years, and it must be 10K light years thick on average so 3.14^14 cubic ly... stars seem to be much more densely packed on average than 1 per cubic ly but if we assume that Sol is the measure then the nearest star is not in a 16 cubic ly volume - so we could say 3.14^13 ish stars as an estimate. So I'd be guessing many more than 300 bn stars in the galaxy?

Google says 250 +/- 150 bn. I think low...