I think the 10 cas goes for at least 13BTC
I think the bitbills collection goes for on average slightly overload value.
The bitbills are slightly harder to pin down, less well know and recognizable then the cas.
Either way this is quite the horde in terms of BTC and crypto history.
Considering the last two 25 BTC Cas to sell on their went for only ~$50,000 over premium (less if you factor in the forks) (not accounting for buyer premium) 2-3 BTC over is probably correct.
https://www.greatcollections.com/record_coin_prices.php
Edit: looks like prices might include premium, so technically they really sold for under BTC value?