If I sell a bow for 30 gps and I note two of those bows, is that worth 60 gps in the general store?

Well you can't sell noted items to the store, unless they are in one, five or ten. However, sometimes the price of things in the store decreases as there is more of them. Eg. First bow may sell for 30, second for 29 etc.

if you sell 2 bows to the general store you get as much if as you sell them noted