These ex us military boats are generally sold by www.govliquidation.com
. If you are in the USA it is worth keeping an eye on the site - they have sold many 5.4 avons too. Generally for no more than 1000usd with console etc. Sometimes they even have new tubes for sale in the same sales. Not much use for us brits though!
As for the one that you see on ebay, it isnt worth much. The tube repair will be the problem, and for a 4 metre boat that probably isnt going to be worth that much money at the end of the day. If you are going to bid on it, make sure you check to see if there are any other cuts on the tubes as it could then turn in to a real challenge when you get it home! Good luck!