I'll just summarize.

The mechanism is micropayment channels. Any two between nodes can set up a micropayment channel between them for handling the actual payments.

All that's left is for the nodes to figure who gets paid and how much. So, some kind an accounting system.

What nodes want to obtain is relevancy, as defined by access to the most recent transactions.

They keep records of which transactions they've sent to each peer first (before the peer sent the same transaction to them) and vice versa. Only transactions that eventually make it into a block count.

Based on this accounting, each node knows if it is more relevant, less relevant, or equally relevant compared to each of its peers.

It uses this information to decide whether to pay a peers, or to charge a peer, or if no net payment is appropriate.

Then it's a matter of each node haggling with its peers, attempting get the best price for its relevancy from the nodes it is charging, while minimizing the amount it spends on the nodes which it pays.

Nodes would also want to improve their position in the network by competing for low-relevancy nodes (source of revenue) while attempting to find equal relevancy peers to lower their costs.

The net flow of funds from the bandwidth-consuming nodes to the bandwidth-supplying nodes means that you can achieve price discovery for bandwidth and compensate the providers for the costs they incur.