I'm not going to defend the Joycon prices because I do think they are ridiculous, HOWEVER to be somewhat fair some portion of the market Nintendo is aiming for are going to just be buying the system to mainly use as a handheld for themselves and therefore will have no reason to buy extra Joycons.
Also if the Joycons individually really do work comfortably well for multiplayer gaming, buying an extra set of Joycons for 79.99 would hypothetically be providing you with TWO controllers so you then could play with up to 4 people (when including the original set with the system in mind).
I think what you have to understand is that most likely that is how Nintendo is selling them.... essentially as the extra set to buy if you want to play party games with a group.
I do think the comparison is poor though with the Move controllers. I don't particularly care for or like the fact that Nintendo has made the Joycon controllers somewhat advanced and complicated as far as features, BUT there is no doubt that they do indeed include some pretty new tech ideas for home gaming. In particular the motion camera thing and the advanced rumble. Personally I'm really only curious about the rumble feature and how advanced and nice it might be for immersion in certain games I'm playing traditionally, but still, for some there might be value with all of the features
basically in the end the reality is its possible that for WHAT THEY ARE the Joycons are not necessarily that overpriced. However, that doesn't change the fact that possibly Nintendo should or shouldn't have went with an expensive controller like that or the possibility that Nintendo should have had different options for bundles that included more basic Joycon controllers versus the higher tech ones. Really the effect the price point will have on whether consumers pick up extra accessories is the mystery, I suppose we'll have to wait and see. And a lot of that will end up having to do with whether or not Nintendo releases games that really take advantage of the Joycons. Not necessarily with the motion camera stuff, but particularly with the advanced rumble sensors