This is, for better or worse, exactly the opposite of how customers actually think.
That said, there was a recent blog post about how one HNer dramatically increased his revenue by changing his pricing model. Rather than charge for features, he adopted a few tiers of service, each one targeted at one type of customer's use case.[1] I don't know your exact situation, but that might be worth trying as opposed to configurable add-ons. In general, speaking in the language of use cases resonates with the buyer more, and is more likely to result in a purchase.
[1]: http://www.extendslogic.com/business/what-i-learned-from-inc...
When I decide whether or not to purchase or subscribe to something, I do the math to figure out which is cheaper in the long run. That being said, if the price difference is negligible and all else is equal, I would probably opt for a recurring payment.
Is it because a recurring payment implies they only have to pay as long as they are using the product?
I used it for the website: http://http://metalranchandfarmsigns.com/, which on average before Google killed me made $200 - $300.
In any case, my thinking goes like this: If I had to buy SEOmoz in one lump sum for rest of my life the value of the product to me is probably close to $5000. That's what I'd pay for a lifetime subscription just for MRFS.
I can either pay $5,000 (hypothetically) and have it forever, or slowly enter in at $99 a month. If I cancel within 4 years I win, if I cancel after 4 years SEOmoz wins.
I cancelled in a few months.
