It's even possible that if their average cost to support a user is high enough that they would have lost money on the larger volume / lower price combination.
If they have little or no cost to support a user though, then they likely missed an opportunity.
It's very easy to say what you think the price should be, but the preferred method is to empirically test it and get the optimal value that way. It's a lot easier for the OmniGroup to run a sale and test the change in sales once they have some baseline sales numbers. In almost all cases it's better to be on the high side of the optimal price point and come down to it.
For those interested in starting their own company, it's easy and tempting to start with too low of a price. That low price diminishes the value of your product in the minds of the customers and it is really hard to increase your price later.
Anyway, those are my 2c, and for the record I'm one of those who bought it at the higher price.
It'd be interesting to see if a lot of money was left on the table when the iPhone app price rushed to $0.99 in the name of volume over long-term profit. Certainly a win for Apple in gaining end-user adoption of the store and showing that it's a viable marketplace, but I can't help but thinking value isn't being captured by price (a lot of iPhone apps cost less than a disposable, bottled soft drink).
I'm sure they know what's best for their business and price accordingly, but personally the only software I own from them is OmniFocus. The reason I haven't bought more is nothing special--cost vs. utility. I'd love to use more of their stuff to enhance blog posts or presentations, but I don't see it happening their $50+ prices unless I have some very specific business purpose or I have a lot more disposable income.
Anything that helps establish a standard of apps actually costing enough that I can run a reliable business off of the platform is better for me. I'm interested in developing for platforms where I can create a sustainable business, not a hit based one, which is exactly where lower than sustainable app prices lead.