Investors might pay $200k for half a restaurant or some other business like that, but not a startup.
I have seen the show and my observation was: The dragons are really mostly into funding sauce-makers, innovative clothing accessories, etc. and they apply the same principles to startups -- doesn't work well.
I've never seen a startup accept funding from them, its either an inventor who gets access to a particular store or a mom & pop shop.
http://www.youtube.com/watch?v=Z9EkablfWVk - Part 1
http://www.youtube.com/watch?v=lj8MNEgiDTU - Part 2
They tried to counter at 30% but decided to take the $200k / 50%
As funny as that whole thing was, the prof was right to break that deal. This company wouldn't have gone anywhere anyway with that kind of a structure.