But is there additional value in more (proof of) work or are the returns diminishing? In economic terms the best network hashrate would be the one that is suff

But is there additional value in more (proof of) work or are the returns diminishing? In economic terms the best network hashrate would be the one that is sufficiently secure to protect against bad actors but uses as little electricity as possible. Anything more than that is waste, not added value. Edit: typo