*** Update *** - if you are an online or offline business shopping for an interchange-plus merchant account, you may want to check out Transparent FS - they have a cool looking service where they get merchant account providers to bid for your business.  They seemingly have software that lets you compare bids using different pricing structures (ex. 3-tier or interchange plus) to each other.  I have heard of people getting good deals there - give them a shot and let me know if they are any good. 

Interchange plus is the most transparent form of pricing for Merchant Account services.  Interchange is the cost that your Merchnat Account Provider gets charged by VISA and Mastercard.   For a complete description see our article "What Is Interchange ".  Interchange plus means that the Merchant Account Provider passes through whatever they are getting charged plus a markup for their services.  Depending on the size of your business you can get a markup anywhere from 0.05% to 1.00% plus $0.02-$0.20 / transaction. 

Historically only the biggest merchants with the most negotiating power were able to get interchange plus pricing but the market is getting increasingly competitive and merchants are becoming better informed due to the internet and smaller companies are now able to negotiate in this way.

With Interchange Plus you even the informational playing field and can focus on negotiating and shopping around 1 number, the markup, and can bid the processors off against each other (taking into account that different processors offer different levels of service).  I highly recommend interchange plus pricing.  For an example of how much more transparent interchange plus billing is, see "Reading an Interchange Plus Merchant Statement".