'Interesting' Pricing Strategy

I just read, on the PlayStation blog, that the 2 new Resistance: Fall of Man online maps are coming out tomorrow, via the PlayStation store (these were supposed to launch a few weeks ago, while I was still in PS/3 Saga Hell and not paying much attention, but they ran into last-minute problems and had to delay the release until now).

I see that the approach they're taking is to sell the 2 new maps for $7.99 (for the pair). While I don't ever want to be among those who expect to get everything for free (pirates, typically), new maps for an existing game that cost about $80 to buy in the first place... ought to be free! I realize that hardworking game developers and testers spent valuable time getting these maps ready for production (twice now!) but the reality is that it's in their best interest to keep everyone playing the game online as long and as much as possible. More copies of R:FoM get sold in stores or online, if people are showing their friends how cool it is and raving about it at work/school. Before too long, they'll have a Resistance 2 game that they want to sell millions of copies of, and more copies of that will be sold if most people who purchased the first game played it tons.

So I'll be passing on these two new maps, and probably playing less of the game as a result. I suppose it's possible that the maps will be offered for free later on, but then what would that say to the people who forked over $8 for them? It just seems like a poor strategy to me, and one that conveniently overlooks the $800 investment for the PS/3 in the first place and the $80 expense of the game itself. Nickel and diming the gamers who've already spent all that cash just doesn't seem like the wisest course to take. Am I wrong?