You ignore the fact that speculation adds significant demand in itself. If speculators can be seen to make money, more will join the market. This drives demand

You ignore the fact that speculation adds significant demand in itself. If speculators can be seen to make money, more will join the market. This drives demand beyond what would be present if only owner-occupiers and landlords were buying. And what’s more in some markets like London it removes real-estate from use entirely as investment properties sit empty. Your idea of a ‘true’ price is silly and part of the reason prices may go up in future is indeed the presence of ever more speculators. As they drive prices up, people end up paying more for smaller properties, stretching out their debt load just a little further, and raising the whole market. There is no ‘True’ price.