I use EZ Claims Advanced software and in this setup they charge $100/month for unlimited electronic claims submission through their clearinghouse Capario. This fee also covers unlimited support and software updates.
You can send secondary claims electronically for Medicare, Blue Cross and Medicaid.
Paper claims are extra per claim but I don't use this service and I don't know how much they charge.
Interface is very friendly and simple. Initial setup requires some time but overall I am very pleased with them.