You could not commit charity without also asking them to have sex with you (or work for minimum wage for you).
That's the rule of charity that I live by. But ofcourse people have different definitions of exploitation, because like 'evil' its a pretty nebulous word.
Well, you can either feed them for free, or if you DO want their work, pay them a fair compensation, even if you can get away with paying them a near-substinence BS wage.
Feeling good with yourself with paying a BS amount because "at least I gave them work and they won't starve this way" is the basis of modern exploitation.
Sure, what's "fair" might not be scientifically and mathematically derived value, but it's not like it's totally opaque either. If your company is enjoying large profits, you pay your execs top dollar for their golden parachutes, and you are paying your employess just enough to live hand-to-mouth, then increase that.