No thanks. I would much rather people downvote me when they disagree. If all I get is upvotes then what purpose would it serve to be here? That would imply we all think alike which would be silly and dangerous.
It's not for your comments. It's to promote a post for something that you think will earn you money (or something) if it gets a lot of traffic from HN.
I doubt this is being used for comments. Hitting the front page of hn with a blog post or product launch is quite valuable - that's what people will be paying for.
It's pretty obvious the benefit that a poster would get from upvotes. It doesn't take many to reach the frontpage and it's a guaranteed massive increase in traffic to your product.
At $40 for 50 upvotes it's hard to NOT buy upvotes for a small company trying to acquire customers.
It's not for people who post personally to pad their egos. It's for marketing tech products and especially new SaaS platforms, to gain initial traction or give the appearance of an established and active community around it.