Many entrepreneurs who walk into the tank on ABC's "Shark Tank" with sky-high valuations climbing into the millions are often confronted with raised eyebrows, lots of questions and much push-back from the sharks. On Sunday's episode of the show, a vegan dog treat company did just that. But this time, it scored a whopping half a million dollars worth of investment from Mark Cuban.

Ryan Bethencourt, the CEO and co-founder of Wild Earth, was seeking $550,000 in exchange for five percent of the company. Wild Earth is a tech startup that has developed clean, vegan protein treats (no fillers or fats) for dogs. The main ingredient in its treats is "koji" (a fungi superfood), which is its lab-grown protein that includes the 10 essential amino acids that dogs need, the company says. The startup plugs itself as being better for dogs and the environment.

"Essentially, you're forcing dogs into vegan-ship whether they like it or not," said Kevin O'Leary.

The sharks bit — literally — and tasted the dog treats themselves. Lori Greiner described the treats as tasting like oatmeal. During his pitch, Bethencourt said Wild Earth is prototyping the dog food and gearing up to release its treats.

The sharks stopped Bethencourt in his tracks when they asked how he could value the company at $11 million if they hadn't even released the product commercially yet. Bethencourt explained to the sharks they did a lot of research and development to ensure the product will be a success. He said that the company has taken in a total of $4 million in investments so far, including one from billionaire Peter Thiel.

O'Leary, who said he was skeptical of the valuation, said he was out — along with Greiner and guest judge Matt Higgins.

Daymond John, an investor in grain-free, natural dog food company TurboPup — also said he was out, but did leave Bethencourt with one piece of advice: "In the interest of America, I don't want you to ever, ever, ever, ever, ever, ever, ever, ever publicly give that valuation again," he said. "Because you're ruining people."

Cuban, however, remained interested. He made an offer of $550,000 for 10 percent; double what Bethencourt was originally seeking. Bethencourt tried to negotiate, but Cuban wouldn't budge.

"Mark, I'm willing to do that, even if that has to come out of me," Bethencourt said, finally accepting Cuban's offer.

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Disclosure: CNBC owns the exclusive off-network cable rights to ABC's "Shark Tank."