Are you sure it's not the whole account. This is what it says.

eBay Money Back Guarantee

If a buyer opens a case through eBay Money Back Guarantee (because they’ve not received an item or got something that wasn’t what they ordered) we’ll ask PayPal to hold your funds while the case is open. The funds will be released if a case is found not to be the seller's fault.

If eBay is asked to step in and help and we decide in the buyer's favour, we will give them their money back. To do this, we may reverse funds held in your PayPal account back to the buyer, or pay for the refund and then seek reimbursement from you (either by debiting your PayPal account or adding a charge to your monthly selling invoice).

Your PayPal account can be on hold for up to 7 days.