Typically for my base 1 hr photo session, with viewing gallery, people have been ordering between 100-250 worth of products per shoot.
Okay, I looked again at the heading of the forum topic: The Business of Photography. So my remarks are from the standpoint of running a business, and one of the characteristics of a business is that it makes a profit above all expenses.
I strongly suspect any photography business requires more than 100-250 dollars to make a profit from a 1-hour photo session, with true expenses and actual billable hours per week correctly calculated.
In the portrait business, a guided sales session will result in greater profits than simply posting images online and waiting for someone to bite the bait. Your current method is no money up front, no minimum package in the middle, and haphazard sales in the rear. You're not controlling your sales process at any point. That's not conducive to running a successful portrait business.
I would recommend either a session fee or a minimum package to at least cover your costs in producing the session so that you're not actually losing money on any sale. You are producing a custom product, which means each job costs you money up front for a product you can't sell to another customer.
The size of your session fee, if you go that way, depends on your sales model: A small fee if you want to depend on greater print sales, a large fee if you want to continue with online sales and CDs.