It is just general demand, really. Every step of the way can charge more, as compared to 15 years ago, because people are willing to pay more for their services.

Like the headline suggest, the solution is to increase supply. Except, not of houses, but the inputs that go into houses (materials, labor, etc.). Until supply is met there, the cost to build cannot come down, and until the cost to build can come down used homes cannot come down either. Alternatively, we could stop wanting so many houses, but that is likely less practical.

As mentioned, if you get all the software developers building houses instead the price would drop pretty quickly. But... good luck convincing them to do that. That is what has to be overcome.