Maybe I can add a little more info?
You need 1 fruit and 1 sweetstuff for making one Nutrio bar.
You cannot mix different kinds of fruit, so if you start refining, it would make most sense to have at least 1k of one kind of fruit and of course the same amount of sweetstuff.
According to peauction.com the price for sweetstuff atm is 120%, TT is 0.01, and a piece of fruit costs 0.02 PED (TT is 0 as for sweat or dung).
If you refine now for example 1000 sweetstuff and 1000 Papplon you will have a market price of 12 PED for the sweetstuff and 20 for Papplon. This makes a cost of 22 PED for a Nutrio Bar, which is 0.01 TT and therefore a cost of 220% refining it.
If you now want to sell it, because you sold you pet or refined too much, of course anything under 220% would bring you a loss.
Have fun refining!