Wealth is not stuff. It is the intelligent arrangement and usage of stuff. Infinite wealth is possible from even tiny amounts of raw materials - it is just harder.
So wealth = intelligence * stuff. Since stuff is obviously finite, I guess you are asserting that intelligence (or technological know-how) is infinite? Even assuming the upper limits of intelligence is unbounded (very doubtful), it is demonstrably not today.
"If I have seen further it is by standing on ye sholders of Giants" -Isaac Newton
I need not be smarter than Einstein and Isaac Newton to improve things further than they did, I need only leverage the knowledge that they added to the public sphere and add a bit of my own insight to increase the intelligence portion of your formula.
Then again, there are other multipliers that are hidden in your formula. The printing press, assembly line, electricity, the telegraph, the computer, robots, and the internet all add their multipliers under the intelligence factor as well.
Collaborations across continents allowing specialists to work together across several fields allow several individuals to add together their insight to increase the value of that factor still further.
Using the same volume of seeds, sunlight, water and labor(including oil), a modern farmer can leverage greater understanding of both the weather as well as the exact nature and condition of their soil to produce a better crop than a farmer using cruder tools and methods. This includes sustainable methodologies that would keep a given patch of land producing after old methodologies would have made it useless.
While only a singularity type occurrence would allow the intelligence factor to get close to what we would consider infinity, there is no reason to believe that there is any upper bound on it when it continues to grow at an ever increasing rate.
Once that factor gets high enough, the cost/profit ratio of things like mining the moon or harvesting comets and asteroids becomes worthwhile and we will not even be restricted to the paltry resources of this one little rock.
And the best way to increase that Intelligence term still further is to give people the freedom and motivation to innovate.
The argument for a strict limit to wealth requires that a masterpiece by Leonardo da Vinci be worth no more than the paints and canvas that he started with, or that a computer processor be worth no more than a bit of dirty sand, or that a concert written by Mozart be worth nothing more than a blank piece of paper and a pot of ink.
Forgive my ignorance, but I just cannot see how that could be the case.