I highly recommend, as a business model for accountants and bookkeepers, that you price based on a fixed monthly fee, and include the cost of the apps. I cannot tell you how many times, a prospect who is hesitating about my fees, comes right over the edge, when I confirm that the cost of QuickBooks Online is included in the fee. Assuming the client has added me as the Master Admin in their QuickBooks Online company, then it is really easy to move QuickBooks Online clients to Wholesale Billing.