they won't be equal because not all ubi income will be spent on consumption. it will stimulate consumption, however, which was the primary reasoning behind the op and that will lead to some form of inflation edit: inflation because based on the assumptions of the op, the supply side has stagnated and so there is less downward pressure on aggregate prices. the degree of that inflation is unclear and i'm not familiar with any empirical studies. either way inflation won't match one to one with the increase in income.

fwiw i noticed above you mentioned that there will be an increase in productivity, wellness etc. although i tend to agree with the wellness aspect (esp. compared to our current circumstances) the degree to which wellness would increase is also unclear. for some colinear studies, i'm thinking of finkelstein's work on medicaid expansion in oregon where they found exposure to medicaid increased reported well being of recipients.

and i don't think productivity increases under a ubi holds water on theoretical grounds.

you seem to be assuming large increases in productivity and wellness and other benefits and then asking if inflation will erode that, when we also need to consider that the possible benefits will themselves be attenuated, particularly for those already at lower incomes or those who will earn a ubi.