UBI is implemented tomorrow. Every citizen gets $1000 per month.
Landlord now knows you have an extra $1000 that you never had before. Why wouldn’t the landlord raise prices?
Now you have an extra $1000 a month and instead of eating rice and beans for a few meals you go out to a restaurant. The restaurant owners know everyone is eating out more so why not raise prices and maximize shareholder profit as always. The restaurant/corporation is on TV saying, “well, demand increased and it is a simple Economic principle that prices had to increase. There’s nothing we can do about it”.
Your state/country has toll roads. The state needs money for its deficit. UBI is implemented and the state/country sees it as the perfect time to incrementally raise toll prices.
Next thing you know UBI is effectively gone because everything costs more and billionaires keep hitting higher and higher all time net worth records.
In your hypothetical, the market just jumping in cost like that creates opportunity for competition in the market. Because everyone who could not establish a biz charging X can get into the game charging between X amd X+Y, undercutting the gougers and driving prices lower over time. Theoretically.
Which is why capitalism only works if it’s paired with strong anti-monopoly regulations.
In the current environment, damn near every good and service is cornered by a small number of companies, sometimes only one. So while all restaurant prices probably won’t go up, all vehicle prices will.
Hell, with this whole “inflation” bullshit we’ve seen that the entire economy is happy to influence public opinion to allow for an orgy of price hiking. Not necessarily in a coordinated way, but not not in a coordinated way.