Yes, it's definitely 'middle class'.
$500K/year is mid-range doctor salary (some earn much more) - it's enough to have a nice house or flat (probably in an expensive area - meaning that its' not even that nice, just has a good location), nice cars, travel, a cleaner, pay for your kids private schools, and have a cottage/second house.
But not that much more than that.
After all the 'added expenses' of a upper-middle-class lifestyle, they can sock away some money, but not that much.
I know several families in this range and you would not consider them 'rich' by any means. They're just 'well off'.
To be 'economic upper class' you'd have to be way past the many millions in net worth. I'd say more than $20 million at least. Probably more.