Unfinished product has no value so finish it for 2 reasons 1. Probably you will get good number of users which might boost your motivation again. 2. If #1 do

Unfinished product has no value so finish it for 2 reasons 1. Probably you will get good number of users which might boost your motivation again. 2. If #1 does not happen then you can always sell this product to someone else(flippa.com) which will at least pay for the time you have spent on it rather than totally throwing it away.