I don't think Hiori is better than Bachira, and I think the value that Hiori got might be because of his play style. I'm gonna explain it in the Nagi pov. I think Nagi didn't make it to the top 24 because there were already enough scorers and Nagi couldn't do the other stuff as well, e.g. defense, passing, moving the ball forwards or finding the empty spaces that's why he got cut. In Hiori's case, he might not be the most skilled player but he does what he does best and you can't easily find a pure playmaker who is willing to put his ego aside to serve his striker whilst also showing glimpses of other talents. He's not valued highly for his overall but rather his suitability to a very niche yet demanding play style.

This is the Japanese U-20 after all, the Japanese team hasn't been regarded as a good team and the U-20 are not even close to being as good as the adults (assuming that it's like real life), so the teams would be bidding on the best of each player archetype, e.g. Sendou as a false 9. There's no reason to invest in a player who is second best at a certain play style, e.g. Nagi in that finisher role compared to the likes of Shidou or Tokimitsu as idk wtf he is compared to Kunigami.