How many items can you sell before you should pay vendor fees?

I for one bought a couple cars that were filled with parts and to offset the cars I sold off the extra parts to create one car and purchase other parts to finish mine off.

If I didn't sell on here I would have tried to have sold in my local chevy community or scrapped the parts to get the cash.

Also the fees on ebay got too expensive so it has basically died.
Kijiji is headed in the same direction if they get too greedy