Grade B commonly has scuff marks (not major ones) and the logos may be slightly worn.
Here is knet's description of Grade B:
I believe that this is very representative of what the Grade B is - I have some here in my hands and they compare very well with that statement.
If these prices are too high, knetgolf commonly has promotions on certain brands of balls. Currently there is 15% off all ProV1 styles, 30% off Maxfli and 20% off Distance Balls. These types of sales usually allow anyone to find a ball that fits them for the right price.
Hope that helps, if you have any other questions, let me know.