This is no different than a pure constant. If fact, it’s literally identical.
tx.price is zero or something less than it should be, there must be an ethereum miner willing to take the opportunity cost of mining such tx instead of another. As a result, the attacker might have to cover the opportunity cost for mining such tx. (well…there is a potential cost difference on the opportunity cost here vs the cost to perform challenge so it is not perfect.)
You need to make sure that you’re setting up the bond structure such that it’s impossible for the operator to guarantee receiving funds at the cost of their bond
I am lost here actually. Whoever is acting validly would never lose the bond, the opportunity cost would be some interest rate time to lock the bond in the contract. Meanwhile, I am not really sure why you mentioned operator here. I am guessing you’re talking about the scenario operator mines invalid tx and tries to exit with that, so other users need to challenge (?). However, that is exactly why we want to cover the real challenge cost as much as possible instead of having some constant value. The closer it is to the real cost of challenge, the lesser challenger would give up challenging due to the challenge cost > fund losing.