Sorry for the bad info Frank. IMHO both solutions are strong, very flexible, but way to complicated for the vast majority of DNNers and too pricey as well. I didn't spend much time researching them to be honest.
In reading this thread though, I like Caddy's suggestions of having a "limit" of some sort on the number of products a store could have, and an upgrade price to gain access to have more products listed in the store. I have seen that licensing model on other systems outside of DNN and it seems to work well for them.
I know I'm sort of cutting my own throat here in suggesting anything other than low priced, unlimited sites as a licensing model, but I believe a good programmer should be compensated. That said, there has to be an "entry level" of some kind so people will buy the product, and an "upgrade" of some sort so you can be paid properly, even on this version.
Limiting the number of Sites in an Instance still seems to me a workable solution. If as a site creator and "host" of sites in my DNN Install, I can't get a few buck per store, something is wrong. Everyone else is charging for them. Godaddy, for example charges a monthly fee for use of their store. They have three versions. Economy version (20 products only) at $9.99 per month with discounts for longer subscriptions. Same with the Deluxe (100 products for $29.99 per month) and the Premium Stores (unlimited products $49.99 per month). Theirs is also restricted by storage size (GB) and Bandwidth. The more expensive two having a Quickbooks integration feature.
Your imagination really is the limit here on pricing models. Personally, if the "market" can bear the price, you should be able to charge it. Unfortunately, we operate in a market that is spoiled by freebies. Though I will admit that is part of what attracted me to DNN.
Frank, God bless you my friend. You have a great product and I hope you can figure out a strategy from all this that serves the community well, and makes you rich at the same time.
Clay