Baby bettas make me laugh. Although I have paid 20 + for "designer" bettas I honestly don't really think twice about big box stores keeping bettas in cups. I rarely see them stay there for long. They, as products, sell like hotcakes.
In my experience this is untrue. This past summer I helped my friend set up a small fish tank, and we went to Petco to get some basic supplies for the tank. When he was ready to get a betta for his tank over a month later, we saw a few bettas there that had been there during our first visit.