Alternatives do have a cost - and the present way of organising things means that the cost paid by motorists for burning petrol is vastly less than the true cost.
Most of the cost of petrol is shuffled off onto people who don't have an effective voice, people in poor countries, and our own children and grandchildren.
If we had to pay the true cost of burning fossil fuels it would be so high that we would be effectively looking for alternatives, and paying for the cost of developing them.
In principle the best way would be to levy a charge on fossil fuels which would be exclusively used for these kinds of thing. The trouble is that this seems to be politically impossible, and this years brouhaha in the United Kingdom is an example of how it can backfire - though this was made much worse by the fact that the increased cost of petrol was not being used to pay for developing and supplying alternatives.
Probably the best hope is that, even with the unrealistically low price of petrol, viable alternatives and changes in society will be developed which will in fact ultimately drive it out of the market. Solar power, wind power, wave power, biomass (especially biomass) - all of them have the possibility of providing what is needed, together with electric cars, home-working, imaginative public transport and so forth.
The most optimistic thing I ever heard about all this was the Arab oilman (I forget his name) who pointed out that the reason people moved out of using the technology of Stone Age was not because the stones had run out.