This, in fact, is an excellent question for the long term. Up to now, the price points for available online content (music, apps, games, ...and watch faces) are as you said $1... $2... maybe $3 or higher. Exceptional apps have successfully broken into free and pay versions. For example, Dark Sky weather is free but if you want the animated in-bound precipitation graph you need to buy the pay version $3.99. Everyone I know has the pay version. So I guess it's important enough to spend the money.
When pursuing my Project Management Professional certification (PMP) I downloaded some of the PMP exam prep apps. The one I ultimately used was $32. That's a lot of money for an app in a $1 world. Still, the free apps were all garbage. And in the shadow of the boot camp course that's $2,500, the $32-dollar alternative didn't seem so bad (and I passed the ridiculous exam).
For sure, we've been coasting on the techno-geek side of the wristwatch scene where the manufacturers have largely been the electronics giants - Sony, ASUS, Samsung, Huawei, etc. However, I think you're going to see a huge uptick in offerings from the manufacturers on the jewelry side of the wristwatch scene (Fossil, DKNY, MICHELE, Coach, Michael Kors, etc). It's only a matter of time.
So when Rolex and other luxury mfrs finally get completely in the smartwatch groove and start offering optional watchfaces, do you think someone who spends $8,000 on a high-end smart watch will have a problem spending $10 to $50 on one downloadable watchface from the same brand? Probably not. I think when we get to that point, it will dramatically change the market dynamic of downloadable watchfaces which will affect pricing - hopefully in a good way for us developers .