Actually, the effect is much more exaggerated than you are suggesting. According to Tim Rogers, the mythical average player pays $1.70, but it's really made of 95% of people who spend $0, and a power-law-esque distribution of people who spend >$0 to hundreds or thousands of dollars.[1] Most of the money is made off of "whales." Technically he's talking about social games and not mobile games, but it would be surprising if the economics were significantly different given that the mechanic (pay to make things go faster) is identical.

1: http://insertcredit.com/2011/09/22/who-killed-videogames-a-g...