Airlines don't make sense!

First of all, prices continue to go up and down. I don't see why there isn't just a price for a flight and that's all there is to it. I guess that would be too simple. Okay, then. That's just the way it is. But here's a new one for you — If you want to fly from San Jose you have multiple options. Most of them are direct flights and a handful have one stop, but you can also fly from San Jose to Mpls to Detroit and back to Mpls for a few hundred more than just purchasing the direct flight! I guess that's for those people that just can't get enough flying or something like that. If anybody has an explanation for the crazy airlines, please, I'd love to hear it!