I print in PLA all the time. I'm actually starting to prefer it over ABS. The actual volume of plastic that the case uses depends on how much infill you slice it at and can be calculated by your slicing program. In general, you should be able to print several cases per pound of filament depending on how you have your printer tuned and whether you have occasional print failures or not. The case that you are asking about measures around 120x105x35mm. The case for the new boards is slightly smaller.