Yeah, they can weigh up to 2000lbs with a king-size bed. A king-size bed is 6,080 sq in.
A fridge can weigh 300lb being 36"×30". 1,152 sq in.
Fridge is .26 pounds per sq inch. A water bed is .33 pounds per sq inch.
So while heavy the weight is distributed basically like a fridge. This is assuming an empty fridge.
As for durability, a quality waterbed mattress is thick. You aren't going to pop it or cut it without deliberately trying to.
Even if you took a knife and stabbed it from the top, it's not going to leak until you put weight on it.
"Saving tax dollars"
The sheriffs and everyone involved in this program are probably not worth the work of involuntary workers
Spending a dollar to make workers do 50 cents of work