Simply put katana, tachi, and tanto command the most money and are the most collectible items typically. Even though they’re smaller than wakizashi, many top smiths only made tanto and many national treasures are tanto.
the same can’t be said for wakizashi. Hence the difference in price. It’s not about the amount steel but the original intent and artistic/functional execution of the smith.
tanto usually are ubu and retain their mei and we don’t have to imagine much if the tanto is healthy. It’s all still there.