A free list gathers open addresses that anyone uses. They are already on every blocklist, they record what passes through them and they die without notice. There is nobody to complain to.
What paying changes
Here the address is yours, alone on dedicated or with three at most on shared. The list stays up for the period you paid, replacement swaps whatever dies and there is someone to answer when something fails.
The cheapness of a free list gets expensive in the first hour lost to a dead address.