People are free to try offer better deals and services though often times they'll likely be much worse.
Offering better deals in this area almost always means offering horrible services.. I don't think it is fine to do this, especially not when the user was already hired. If you allow this, then you essentially allow users to do this out of spite; slippery slope here and there, you reject someone's entry in a bounty because of them being a farmed account: They attempt to get you ("legitimately; by offering "better" services") fired.
It's a shitty thing to do but not illegal. The only issue I would have is if you had a deal with a company and they got rid of you during the campaign just to save a bit of money. That would be a breach of contract.
I think there should be more scrutiny on new managers popping up to run campaigns because nefarious individuals are getting involved and successfully scamming money from people or siphoning off money to their alts, and then there's the shitmanagers who do absolutely nothing about spam and accept and pay for any old shit. If something had been done about these users we wouldn't have even needed the merit system in the first place.