UC Node Checkout for pay to publish user content?
Try Pay-per-node

This module allows creation of a number of nodes of chosen type for some users. It temporarily overrides the node creation permissions and keeps track of the number of nodes the user can create.

It can be used as standalone module or as an e-commerce plug-in. In the second case paypernode can be integrated with Ubercart, providing a new "product feature" which will allow, upon product purchase, to create a number of nodes.