This sounds a bit irrational. Where does "wealthy" start? Mullvad co-CEO donated ~ $500K, would him donating $100K have the same effect? What about $10K? What if a Mullvad _employee_ donated $500K?

What about work in units of median annual household disposable income, which are at least somewhat responsive to the distribution of money?

What % do you think a reasonable voter should accept a person donating to a political campaign before it causes concern about the donor's influence vs the median household's voice?

Off the top of my head, I'd guess 500k USD is about 1000% / 10x median annual household disposable income in SE, which I think would give the median voter pause.

For what it's worth (my own view): I think about 10% (~5k USD) is obviously acceptable, and I expect most anyone would agree that donations at that level are fine. I think your proposed 1000% is obviously unacceptable, and I expect most people would agree with me on that as well.

I'm not sure exactly where the level is that opinion would flip, but I feel pretty confident about those boundaries.

A company shouldn't be able to fire an employee over their opinion,[0] so that wouldn't matter to me. For a major owner, the donation amount starts to matter to me around $5-10K, but YMMV.

[0] I suppose unless they have a very influential position and it's about a matter that contradicts main company goals