Easy.  It's because the control is by far the most important part of any system.  That $500 Denon AVR is pretty useless if you can't reliably get it to work everytime you want it to.   

Now add the other devices it needs to control.  TVs, Cable/Sat STBs, Blu-Rays, Lights, Shades, Video Streaming devices, Whole house music systems, the list goes on and on.

Now you also need the ability to turn on all those devices, set the devices to the proper inputs, set any sound modes, dim the lights, lower the shades, yada yada yada... 

Oh yeah you want all that cool stuff to happen by only pressing one button right?  I sure don't wanna press 10-20 buttons.  Oh yeah, don't forget to put delay time inbetween the commands for everything to work properly. 

Now we'd also like to have the option of using that snazzy RF base station.  I for one don't want an IR rcvr kit and have to point my remote at it for god knows how long.

Add in the ability to make the remote look nice with all the cool graphics.

Also, when your done for the night, you have the remotes charging base to set it into.  Pretty sweet to not have to keep replacing 4 AA or AAA batteries every so often.

A well programmed remote control is an amazingly powerful tool.  Imagine getting a phone call from the mrs. while your at work to try and have to explain how to put on a DVD for the kids.  Well first grab the TV remote and turn on the tv.  Next find the Denon remote and turn on the rcvr to the DVD input.  Next grab the DVD remtoe and power it up.  Oh no, 2 of those remotes had dead batteries!  Damn we don't have the right ones in the house!  Now go  lower the blinds by hand - LAME, and also get up and dim the lights - LAME!

So basically off the top of my head, thats how URC  justifies the price of an amazingly powerful remote control!  Best money you'll ever spend!!!  

That made me feel better! lol