A Glock is basically the original mass produced polymer (I know there were others before Glock); you can't watch a TV show or see a movie w/o seeing a Glock. Lots of young children even know the name.
Most folks want an original (Glock), you have to sell most polymer buyers on an M&P, FNP, XD, etc. Glocks are reliable, don't have any external safeties or buttons to push to make them go. Every gun store in my area has a big Glock banner tacked to the store front. Everybody sells them.
They have held their price pretty well and have good resale. Plus they practically give them away to law enforcement agencies. Yea, I don't doubt their sales are up.
Plus, Obama has been their best sales person for nearly 2 years now.