I sell on three ids. I list up to 200 new items, many with multi varients, in store fromat. I list second hand items at auction up to my free listing limit on another id and finally up to my free listing limit for selected second hand and new items at BIN with best offer. For me this keeps my fees as low as I can, actually lower than a year ago, but of course for you it depends on what you sell, how much you sell and what your profit margin is.

The only way to find out is some diligent work with a calculator after removing rose tinted glasses and being honest about how much you are really making doing things the way you are and how any change would alter the figure.