You've picked by far the most expensive on eBay.
There was brand new ones on eBay for £250 each, from a recognised tyre dealer for a while.
There has been the same pairs of runflats on there for months.
There is more money to be made on eBay selling them than here though. Prices are less here and struggle to sell runflat.
The tread depths do sound very good. Odd to have the perfect 8mm and 7mm elsewhere.
With those depths you will get a really good price, sadly I won't go anywhere near £400 for a pair.
Recently i did buy a pair off eBay but had to send them back as they weren't as described but that wasn't to be known at the time of bidding. 6mm tread cost £200 for the pair.