IMHO, the answer is probably more complex than one thinks.
Demand? With the huge increase in concealed carry, the simplicity and reliability of a revolver is attractive. Also, with the increased availability of good holsters out there, many folks now feel comfortable with a big bore as their EDC. Handgun hunting has also seen a large increase in popularity lately and most folks who think hunting handgun, think revolver, especially for big game. All three may be a subtle increase on their own, but they add up.
Cost? Add demand and you add cost. Simple economics. Plus the fact that most quality revolvers are made here in the U.S., using American labor. Labor costs have increased dramatically lately, especially due to the skyrocketing cost of healthcare benefits. Revolvers due to the amount of parts/assembly and the way their steel is finished takes more labor than your standard Tupperware gun, even tho the advent of MIM has eliminated hand fitting. Revolvers don't seem to get the discounting at the retail levels like pistols either. Probably that dang supply/demand thingy again.