I would say it totally varries by both airline and departure or arrivial city. If for example you are flying say United, from a United Hub, I would expect the number to be much higher then another airline that didn't have that city as a hub. That being based on many people flying from a hub do it often.

I don't get the question though There are actually people out there why fly on an airplane and don't get miles for it

By the way, I too would pay more money to get miles, not really sure how many, but there have been many times where another airline was a few dollars less expensive, and I've said no thanks (though if it is business I will usually only be asked to be reimbursed for the lower cost and kick in the difference myself)