Why hasnt he had these clubs coming after him already then?
Who do you think will offer him a job bigger than the one he has?
It's not about a bigger job though is it.
Managers essentially want to do two things, compete for trophies and compete at the highest level (which in club football is the CL.)
Malaga and Bate do the second, Hearts and Panathinaikos do the first. They're not bigger clubs but they have advantages that Everton don't have (what league they play in, what money they have in relation to the other clubs in that league etc).
I've said this before and I'll say it again. The glass ceiling of CL qualification and cup success that is supposedly there in this country doesn't exist in france, germany, spain and italy to the same extent. So his job will, supposedly be easier (I'm not convinced by this myself, but I can see why Moyes might think it would be).
And even if we assume that he'll never leave england there are at least 15 clubs that outspend us. QPR do. Stoke do, Sunderland do, Villa do, Fulham do, West Ham do. They're not bigger jobs but there might be jobs he thinks will be easier because he'll be working under more generous financial restrictions.