From like when we were kids until now? Not many, at least in terms of who buy the figures.
If MOTU was selling millions of each figure worldwide back in the 80s, and if fan estimates are correct that MOTUC has sold between 10K and 20K of each figure... big difference.
For an example, let's say they only sold 1 million of the original He-Man back in the 80s across the globe.
And let's say they sold 20K of the Classics He-Man, and each went into the hand of a different collector.
The current market would be 2% of the one in the 80s.
Yet since we know modern collectors can often buy more than 1 of each figure, that some are in the hands of retailers and not collectors, and since they undoubtedly sold WAY more than a million of each of some of the 80s characters, that percent is far smaller.
But I'd wager it's a similar situation for nearly every 80s toy line that still has adult collectors.