He posted this a few minutes after noting that he thought 30% was a bit high, so I'm sure he knows.
I think what he failed to understand (not sure what his outlook is currently) is that to provide a payment portal is nowhere near as simple as using a "billing module" anymore. If you want to provide some very simplistic gateway page to paypal or something, that's one thing, but if you want integrated credit card billing and the ability to bill later on, it get VERY complicated. Not only is integrating and dealing with a billing module itself complicated (whenever you are dealing with money have to take the utmost care to do it right), but PCI compliance itself can cause some major headaches. PCI compliance stipulates constraints such as server hardening, employee account password policies, quarterly network reviews for security flaws, etc. Also, on the billing module side, it's strongly discouraged that you keep CC numbers (and if you do, they need to be strongly encrypted at all times when stored). Generally, they want you to use the card in a special transaction, store the transaction reference returned, and use that to tell the processing company to charge the same card at later dates (but there may be restrictions on what types of charges can be done this way, I don't remember). That's an example of the type of issues you need to deal with when correctly implementing a payment processor's billing module. Keep all that in mind when considering the cost of the module (a large portion of the cost may be implementation with your services).
I've been on both sides of that; I've implemented a billing module using their API and SOAP, and I've helped in the review and modification of the network, servers and code to come mostly in PCI compliance (separate project). Believe me, for the vast majority of developers, not having to deal with payment tracking is well worth 30%. If you already have the billing system set up, or need to for some reason anyway, then go ahead, and then release a free channel that requires linking to an online paid account.
-- GandK Labs
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