Don't waste time and money seeking legal advice,  as eBay are in their rights to hold money as you understand,  for selling a high value item.

Any sudden or  unusual activity on an account , such as the selling of a high value item does bring about these security holds , and held until eBay are satisfied that the genuine owner has sold the item,  and the buyer has received item,  and will not open any case.

It is a security hold,  so for that reason eBay will not reveal the length of  time for the hold, each case having its own reason for a short or longer hold.

Sorry, but no point contacting CS,  they cannot tell you when you will receive your payout, and doubt you'll see any movement over a weekend.

@finlay5514