The issue is more that we're currently running out of extractable fossils (net energy peak for oil liquids is projected to peak as early as 2025 and the decline into nonextractability is rapid) so it's a question of having liquid fuels and synthetic stock, at all.
What kind of life style we can expect where hydrocarbons and energy in general is expensive is an interesting question. See e.g. https://surplusenergyeconomics.wordpress.com/ for analysis of that.
He gives an estimate of $130 trillion usd for the global cost of energy transition with a link to the source
... I don't understand how this estimate is made though.
Sorry, I haven't started memorizing Fediverse handles yet. Tim Morgan measures ECoE in percent, and real GDP is GDP minus debt, or x units of debt produce a fraction of that in GDP. Plus ECoE accounting. His model is proprietary, so nobody exactly knows how it's computed but he himself.
That IRENA model seems to link some large spreadsheets and notes on that page. No idea how complete that is.
As to investments necessary, some two decades ago I estimated we'd need some 3 TUSD/year, inflation-adjusted, for the next 40 years to transition. As a rough estimate that's as good as any other guess, not facturing in extraction of progressively depleting resources.