I don't follow your causality there. given how "wimpy" hybrid batteries tend to be, the costs aren't terrible. And replacement is reasonably simple to do on a prius, most people can't even change their own oil though. So using sale cost to infer reliability (when taxi's are going 300k in a prius) is a bit wonky.
How Long Will Hybrid Car Batteries Last? april 2014:
"retail price for a new hybrid battery is
$2589; with labor, it should be less than $3500 total.
I'm not complaining about the low cost, I'll gladly take advantage of it. just not going to agree that it means it is unreliable. The electronic portion is the most reliable part about it.
As for "making sense", it depends on the driver and alternatives. I do better hypermiling with an econobox 5 speed, but do ok with the prius. Have gotten good enough with the prius that the difference is marginal. Your typical driver will do better with the hybrid of course.