Right, well, in the UK.......
CB Radio is pretty much free access, but you need to be (might be slightly out of date here) 14 years old and pay 15quid for a license. You can buy a new CB for about £55, the aerial and mount for fitting to a GS can be anything from £25 to £150, depending on how you want to go about it. Now, since your average CB radio doesn't have VOX (which is virtually useless over 50mph anyway), you'll also need a switch, earpiece, mic etc. But since you'll need at least earpiece & mic with a PMR446 setup, and probably a switch, you can pretty much take that out of the equation as regards cost.
So, you've just spent about £120 on a good quality PMR446 handheld that will get you about 1/2 mile on a good day. Then someone comes along and tells you they spent the same on their CB setup (plus £15 for a license), and they get 20 miles on a bad day. Kinda puts it all in perspective. The only real disadvantage is the loation of the radio. PMR446 rigs are very small, and are handy to stow. Even handheld CB's are a fair bit bigger, and what you get for about £55 is about 6x4x1 inches. Not a problem if you have panniers, you just mount it under the lid. Otherwise it's quite easy to knock something up with ammo boxes, which can also double as lunch boxes etc. (I intend at some point to make a refridgerated ammo or topbox to keep me sarnies cool

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Now, all this does need to be offset against the fact that you can buy a basic pair of PMR446 radios for about £20, and a couple of sets of cells and a charger for another £20. I personally think that anyone who's bought a GS rather than a Tiger/Africa Twin/V-Strom should give plenty of thought about spending GS money and skimping on something that, quite frankly, can save your life. Especially since the greater range of the CB means you're much more likely to get someone at the other end if things do go wrong. And it's also quite cool chatting to some bloke from Poland when the sunspots are doing funny things to the atmosphere
The long and the short of it is that CB Radio is designed specifically as a mobile, large area, medium distance method of communication. PMR446 is designed specifically for portable short range communication within a limited area, and is almost completely unsuited to use on bikes. Manufacturers and suppliers have taken advantage of the traditional view of CB radio (10-4 good buddy), and in doing so have, IMHO, taken complete advantage of their customers by indroducing new, more expensive, and virtually pointless products. You can't even say they exploited a niche in the market: rather, they completely disregarded the fact the niche has been filled 20 years ago and (reoccuring theme here) took complete advantage of the customers lack of understanding in what is, to be honest, quite a technical field.
If anyone genuinely wants more info on radios, aerials, etc., I'll do up a "How to"