According to swissdevjobs.ch[1], the top 10% salary for a senior software developer in Switzerland is 135,000 swiss franc; that's roughly $170,000 per year.
So if this is correct, then even in Switzerland, it seems like $300,000 per year would be an obscenely high salary for a senior developer.
Well first of all it's a CEO position, not an SWE :)
Even if we scope it to SWE, I don't think that's far off the US percentiles.
In London I imagine the top 10% SWE is not even 100k GBP. In Germany even worse.