Unfortunately, most people only see fins and colors and not the whole Betta. And some think if the price is high it must be good. Just look at the ridiculous prices people pay for "Designer Dogs" which is just a euphemism for mixed breed.
It's just terrible. Petstores *usually just petCo* sells EEs like in my avatar for $40! then they have the ridiculous mixes like HMEEDtPKCT male bettas for anywhere from 60-200 on online places and such. People only look at the tails, I agree.
Bettas seem way more expensive here in Oz compared to America so it is not unheard of to pay up to $15 for just a run of the mill veiltail. A HM that is not even of very good quality can easily go for $40-50.
However, even in the land of expensive fish, I would consider $100 for the female in the OP to be excessive.