Content by credit/level in Drupal?
The Userpoint provides a mean to store a user credits and can be combined with the Userpoints Node Access to sell node (ie. content) access in exchange of userpoints (credits). The User points Nodes and Comments allow you to setup automatic rewards for content contribution (ie. nodes and comments creation). But it doesn't seems to provides the rating feature you ask for, nor does any of listed User Points Contributed modules.

What should be easily doable, is to use the Fivestar to rates node and then to grant, and revoke userpoint to the rated node author on voting (hook_votingapi_insert() and hook_votingapi_delete()). By restricting access to voting (ie. the 'rate content' permission or through an hook_fivestar_access() implementation), you can control who is allowed to grant credits to your users.