It absolutely does affect my purchases - I have only room for 3 (sometimes 4) pins, so I have to REALLY really love the theme to even look around. Alien, LOTR and Doctor Who are on my list, but the only one I have a chance of picking up any time soon is DW... except I can't find one.
I would think that the high prices would almost require a licensed theme for this reason - or a deeper discount on an original idea like Dialed In in order to entice buyers. But I guess JJP at least is confident in the sales for DI. Stern seems to be going exclusively down the licensed theme route (have they always done that? I guess so...)