Exactly right: a doctor who earns $500k/annum is working class where a landlord earning $50k/annum is capitalist class. The division between the two comes from whether or not the person sells their labour to generate income versus making money from capital assets without expending labour. It has nothing at all to do with the amount earned.

Now, the truth is that there are a fair few working capitalists - those who sell their labour, then use the proceeds of that sale to purchase capital to gain further income - but that’s where the waters get a bit more muddy. I am one of these people; I earn dual income from my job and from my investments. Many might consider me a class traitor, and there’s a fair amount of reason to that accusation, but I personally consider that I am just operating within the confines of the system I was unlucky enough to be born into. I’ll consistently vote for people who would take away my privilege to capital investments but, until they gain power, I’ll use the current system to my advantage.