Exchanges could potentially perform the following services: introduce buyers and sellers, assist in transaction especially where the material is highly specialized, assist in negotiations and terms, and provide secure bidding and transaction execution.
There are two different ways that revenue can be generated from making an online market. The seller can be charged a flat fee in a manner similar to the way that newspapers charge for classified ads. Alternatively, the seller can be charged a transaction fee based on a percentage of any completed transaction.