Nobody really knows. It has not been proved that useful QC is possible. (All existing QC is practically useless, and it is not clear that it is even possible to scale it up. This is not snark; if it ever will be useful, we must of course walk before we run.) It is possible that there is no amount of money that will make it useful. It has also not been proved to be impossible, and interesting and tantalizing breakthroughs have been made over time such that it's hard to look at them and firmly promise it's impossible, either. (I fall on the skeptical side myself, but it's what I call "true" skepticism; produce it and I won't try to argue out it out existence, I'll just update my beliefs and move on. And celebrate whoever produces it for doing what I believed to be impossible.)

This is rather like commercial fusion research; it has not yet been shown to even be possible to economically use fusion for power generation, yet it has not been proved impossible either. Contrast this to nuclear fission research, which at this point is more like engineering; modulo lawsuits and administrative compliance, we could probably take a pretty good guess at what it would take to, say, bring a commercial thorium reactor online.