Legit. I'm fairly sure their business model relies on getting transactions through quickly, so I would expect them to pay higher than normal TX fees. Do other clients jump to match it?
Not sure what you mean by other clients jump to match? They're welcome to pay whatever fee they like i guess - just seems odd they pay 300x the requirement.
I was thinking "smart" TX fee algo on a popular client resulting in a fee market like gasoline: quick to go up, slow to go down. I think most just go with calculated/estimated TX fee.