[ZenoArrow]

Costs could inflate in the way you say, it all depends on the health of the particular market (e.g. how resistant the market is to collusion/price fixing).

If you wanted a more reliable way to ensure UBI would remain effective, one way would be to treat it as a separate currency that could only be used for the necessities of life. Moves could then be taken to limit profits made on these goods without distorting prices in the rest of the economy. Could also couple this with government support to encourage automation and other savings in these industries. I'd argue both of these changes in combination can result in a UBI system that is protected against price hikes.