Yep, you have to think of that equity stake as the cost for a 5 minute Friday night commercial. I'm assuming such a commercial would cost maybe $30-50k or more, so it seems like a semi-fair deal (although since you are also the one creating the entertainment which lands the sponsor deals maybe not!)

It's better than a commercial. People actually want to watch, instead of changing channels or going to the bathroom.

I wonder if that's unique to Shark Tank. I never heard of it wrt Dragon's Den.

That said, I think if you were really going to go through with that plan you'd probably want to try to find out how often the option has actually been exercised. It may not even be entirely enforceable.