Turn down the deal is exactly what Scott Jordan of SCOTTEVEST did... I'd be curious if he got action on the deal he was trying to make after the show aired. Scott described his experience with Shark Tank extensively on the company's website [1]. The "raw unedited video" of Scott watching the episode he appeared on for the first time is interesting (he gets interrupted with news that the SCOTTEVEST site is not withstanding the traffic surge during the episode's airing!).
Investing at a 10 times profit in a small company is a highly risky investment. You are gambling that the company will be: a) ethical b) continue to operate for enough years to pay you back c) If they stay the same then after tax it will take 15 years to pay back the investor assuming that all the profit goes to paying back the investor which is highly unlikely.
Potential growth is the upside that you are looking for but it's certainly not at all guaranteed, and the opposite is also possible (negative 100% growth, or company being worth nothing).
Who knows; you might ask for the moon and get it.