That would annoy the hell out of me (if done with a fps etc).
"congratulations, you've finished level 9, now pay us £9.99 for the next 10 levels"
yea for an fps that would be poop
but ive been playing infinite dungeon on android.... got to the 10th level "for full game buy here" ad i did... tho was only what £1.50 not a tenner 