HN user
That's why they created DoNotTrack initially. Then browsers turned that on by default, ad revenue lowered, and sites/adcompanies decided to ignore it because it was turned on by default.
Subsidies are fixed costs. They are not investments, they are one time payments. Under certain conditions, you have to pay those back, but these are commonly not related to pricing.
I don't know how much you know about energy grids, but there is a big reason why negative prices are needed. Energy can't float around on the network. It needs to be used (by direct usage, or storage). If there is too much energy on the grid it needs to be used. There's two ways to solve this, being stop energy from being pushed to the grid, or consume more energy. Both lead to negative pricing to create an incentive to achieve this.