[2Pacalypse-]

Indeed. The added option of leveling up your compendium was a genius move by Valve. There is a screenshot[1] of someone with level 1058 on his compendium already. Seeing as $10 buys you 24 levels, he spent over $400 on it.

[1] - http://i.imgur.com/VSPWNDu.jpg

[001spartan]

You can earn levels through playing the game, and earning drops in-game as well. It's not necessarily from buying levels alone.