How can I transfer money from my Apple ID account to an Apple account that I can use on eBay?

You can only use Apple ID balance by purchasing items. It cannot be refunded or transferred except under very limited circumstances:

Check your Apple ID balance - https://support.apple.com/HT202359 -->

"About unused Apple ID balance

You can't redeem or return Apple Gift Cards, App Store & iTunes Gift Cards, or unused Apple ID balance for cash, except as required by law. If your jurisdiction allows for refund of redeemed gift balances, you can contact Apple Support."

"Please note this is understanding that your "Apple ID" Balance is now your "Apple Account" Balance. - https://www.apple.com/shop/help/payments