It Takes As Much Time to Promote A Higher Selling Product

I'm about to go to bed, and perhaps I'm thinking this because I'm feeling a little loopy . . . but it seems that every time I come on here and open an affiliate marketing thread, someone is saying that it takes as much time to promote a high priced product as it does to promote a low cost product. I've also heard many times that it doesn't pay to promote anything with lower than a $20 commission.

I was just thinking that, it's probably a lot easier to sell something that isn't as expensive, because the product turns into an impulse buy.

I know that there is the argument that low priced products devalue themselves . . . but despite the "devaluing", I would still estimate that they would likely sell a higher volume right off the chopping block as opposed to an expensive item.

So, if product A sells for $50 and you get 1 sale a day from it
and product B sells for $10 and you get 5 sales a day from it
and you didn't work any harder to promote product A than you did for product B, wouldn't it not really matter since you'd be making the same amount?

I'd love to hear some opinions on this argument.