Potentially, the labor and skill involved in the production. While speculation does play a part, so does the rarity, difficulty of production, & skill needed in the creation of the art. You may argue whether that justifies the price, but at least there is labor and material evidence, while stocks and property don’t necessarily need any real evidence of value to be valued, especially in our current economic climate.
If Trump drops dead from being old, bully for us. If Biden drops dead but Trump doesn’t we are fucked. That is the issue and risk. That is why we want a younger candidate. Why take the risk when you can avoid i?