Maybe? It depends on scale, I think.
$500 isn't much, but $10-20K is enough capital to start a lot of businesses.
Using numbers from this source and doing a quick calculation shows that US median income is 27.8× larger than the median income in Kenya, so $500 in Kenya is analogous to ~$14K USD. So that scans with my ~10-20K estimate.
Developed countries could afford the equivalent of a $10-20K UBI with equitable taxation models. Most households would end up in a better financial situation net taxes, and those who end up in a worse situation financially are doing just fine. (The US could afford a big chunk of this just from switching to a single-payer healthcare system!)
If you're earning over $1MM/yr, then who the fuck cares if you're only taking home 20¢ on the dollar of marginal income? You can already afford to buy a whole house every year.