I read on Marginal Revolution about a new set of four prizes for scholarly achievement called the Tang prizes, after the cultural achievements of Tang dai China. The prizes are roughly on par with the Nobels in amount (they pay a little more but are awarded only biannually). They were created by a Taiwanese businessman with an endowment of $102MM.
$102MM seems like a sort of low price to me, actually — if you can spend that much and achieve the prominence of the Nobels, that seems like a lot of bang for your buck. There are probably a couple hundred people alive who could make a gift like that without affecting their lifestyle or solvency. And yet very few have done so. The number of large prizes for scientific achievement is pretty small, and the number awarded yearly or bi-yearly very small I think. Hmmm. . . .
I did some Wikipedia research to check my belief that there are very few other Nobel-caliber prizes, i.e. science prizes that pay large awards and / or are regarded as paramount achievements in a field. There actually turn out to be a bunch of other prizes with plausible claims to be Nobel-level, some of which I list below. The Nobel Prizes, though, are seemingly better-known and more prestigious than all of these. Some possible reasons: older; pays more money; covers more fields. Other prizes that might be regarded as Nobel-caliber: Abel Prize (mathematics, one prize yearly, big money); Fields Medal (mathematics, about one prize yearly, small money); Crafoord Prize (science, one prize yearly, big money); Chern Medal (mathematics, new prize, one prize every four years, big money); Kyoto Prize (science & humanities, new-ish prize, three prizes every year, big money); Rolf Schock prize (math & humanities, new-ish prize, 4 prizes every 2 years, small money); Shaw Prize (science & math, new prize, about 3 prizes every year, big money); Turing Award (computer science, one prize a year, paid no money for most of its existence(???) but now $250K). You can probably think of some other contenders: John Bates Clark Medal, Templeton Prize, etc.; this may be a sort of arbitrary list.
So maybe you can’t endow a real competitor to the Nobels for $100MM, because there are a lot of well-endowed prizes out there that have a lot less stature than the Nobel. What do you think?