Sure, but those same free markets will happily see those expensive producers go out of business. In the electricity scenario, that would mean blackouts.

If you triple the price, you don't have a new gas plant appear out of thin air. And the result won't really be lower consumption either, because most people would have fixed rate contracts (not in the UK so don't know specifically, but this is very common elsewhere)

I've read this before and I don't understand how this doesn't become/is untenable.

Doesn't this mean that solar/wind are insanely lucrative?

Also, this would mean that in order to really bring the price down, gas needs to be taken out as a source. But gas is typically the source that balances the grid because its output can be changed quickly. So price wise, you might get a drop but you would lose your ability to react quickly to fluctuations in demand