A typical QMerchant license for one user is $250. This is a one time fee for the software,. The current QMerchant 2015 works with all QuickBooks Pro, Premier and Enterprise versions up to and including 2015. The same is valid for QuickBooks Point of Sale. (They have a different version numbering. The most current one is 14.0). If, by end of next year 2016, your client upgrades Quickbooks to a new 2016 version, then you need an upgrade to a (not yet available) QMerchant 2016 version, which may cost an additional fee. Still this is something in 12 months.
We have some discounts available in case you order more than three licenses in one order. The discount starts at 20%.
We also have a special QMerchant server version available that costs $900. It runs at a server and the users access it as well as QuickBooks via a remote terminal session. The QMerchant server version has no user limit.
For your client, you have to count the number of users / computers, who are using QMerchant. That is the number of licenses you need.
Nevertheless, you can download and install the software. It is fully functional. The only limitation before the purchase and the activation of the software license ist that you can charge amounts up to 5.00$ only.