What conditions were like when Exodus was written is irrelevant. an almighty god doesn't need to alter morality for the times. He could simply command his people to pay the needy for work done. With or without a stable monetary system doesn't matter. To say person A owns person B because A has means and B is needy is wrong. It's slavery. You agreed it is wrong today. It is immoral today. Morality does not change. It was immoral then. Trying to convince you of this obvious fact is like your god performing miracles... it just doesn't happen.
Creationists are like Slinkys: It's hard not to giggle when they tumble down the stairs.