Ahh..Nelle..I miss her!
It's never been my business to ask what other people earn, but considering that Hubpages is just one possible income stream online, no I'm pretty sure Nelle never saw a $5000 month with just HP either.
Most of these guys, Sunforged included, have a wide portfolio.
They may well earn a lot more than this, but not through HP alone.
No I would stick my neck out on this one, and say definitely not on HP alone.
BUT, HP may have given them good backlinks to other places and the combined income may well have exceeded this amount.
Because the people you are talking about were good writers too - what a combo, good writers AND SEO experts.