Why would you buy an expensive router?

Solution
First your ISP provides more then a Router, it also is a modem to use either over the FIOS or DSL (depending on what your paying into). Otherwise the router can't "talk" or modulate the information to transmit/receive over FIOS / DSL without a modem.

Second your ISP provides a LOCKED DOWN device, to keep you from messing with it, and is 'standardized' settings and hardware. Which means that you have no control over it, you can't tweak it for a special need as compared to your neighbor. Also the one being offered may not have USB device support (just plug in a HDD, printer, etc. and instantly shared over the network) and I can guarantee it isn't 802.11AC but the older 802.11n. Also many more expensive ones (like the ASUS) are great for...
First your ISP provides more then a Router, it also is a modem to use either over the FIOS or DSL (depending on what your paying into). Otherwise the router can't "talk" or modulate the information to transmit/receive over FIOS / DSL without a modem.

Second your ISP provides a LOCKED DOWN device, to keep you from messing with it, and is 'standardized' settings and hardware. Which means that you have no control over it, you can't tweak it for a special need as compared to your neighbor. Also the one being offered may not have USB device support (just plug in a HDD, printer, etc. and instantly shared over the network) and I can guarantee it isn't 802.11AC but the older 802.11n. Also many more expensive ones (like the ASUS) are great for gamers to make sure when they are Gaming, and little sister decides to watch the 'funny youtube cat videos' wouldn't suddenly cause FPS drop / hiccups when gaming.
 
Solution
Yea it really depends on what your needs are. It is possible that the more expensive one would not be any better for you. If your needs are simple, you just need internet access and your devices can't support the new wireless AC standard, you may not see a difference.