How much did slaves have to pay to buy their freedom?

The answer to this question would be best said: It really depended on the slave owner. Often the slave owner would want the money he spend -- plus a little more. Often this took many years for a slave to save since they didn't get paid. Often the money they got was from extra work.. they did after their normal work was done.

With that said: Often slave owners didn't see or feel the need to let a slave buy his or her own freedom and would not let him or her buy their freedom for any amount of money.