I don't buy bikes from here to flip but I have from ebay. Usually get bikes with a couple of bits I want, keep them then flog the rest. If I sell bits on here from said bikes I try to price them low or accept low offers. If I want decent money I'd stick 'em on ebay.
I've not got a lot of spare cash atm so things I buy are funded by selling other things. I just fully updated my Orange 5 without spending any extra cash. Didn't want to sell some of the gear I had to though. If I see a badly listed bike going for £25 anywhere but here that has £200+ worth of parts (has happened

) then you can bet I'll flip it. The money would pay for me to make my Orange Elite usable.