I feel the same. On the go a joycon may be acceptable, but at home I'm not interested in playing with a tiny gimped controller. I've read that different modes in MK8 only allow certain controller schemes. One screenshot I saw showed you can use a pro controller or a single left OR right joycon; But the joined joycon icon was greyed out with a slash through it. Which is really odd, so you really have to make a decision.
Assuming everyone has just the Joycons that came with the system, and assuming you're buying for 4 player multiplayer, you need at least:
1 more full joycon controller (L and R) so each person gets a half joycon - $80
2 pro controllers so two play with a pro and two play with a half joycon - $140
3 more full joycon controllers so each plays with a full joycon - $240
3 more pro controllers so three play with a pro and one plays with a full joycon - $210
If you just have a need for a 3rd controller, you can get a single joycon for $50, or a pro controller for $70.
And then there's the grips!!! Another $15 (for one non-charging grip) - $90 (for 3 charging grips). This is seriously a system of nickel and dimes.
Seems pro controllers are the better value, hands down. But then of course early adopters get stuck with the basic grey ones when (speculating) Nintendo decides to released colors in a few months, if you care about that sort of thing. Ugh. I think I've talked myself out of it. Recently we've only ever had up to three people playing at any given time anyways. I've already got a pro controller for single player, so I may just buy a red or blue full Joycon with a charging grip for $110, and get that purchase out of the way. We'd be able to play 3 players with a full controller or 4 players with half joycons.