And if you are released early, somebody else will probably get that bed and they too will be paying the fee. I bet they are double and triple collecting on a significant number of beds.
One problem with tying the fee to net worth is that wealthier individuals may be more likely to have their wealth in trusts so they may actually have "fewer assets" than a poorer person.
Now, if they made the "bed fee" proportional to your net worth, that would be interesting. But that would be Communism, can't have that.