I'd argue that freemium works best when the "premium" part has value for the user. But, making money (i.e. directly contributing to revenue/profit) is just one way to have value. Saving time is another.

So, I pay DropBox not because it helps me make money, but because it's worth the savings in time and frustration trying to come up with an alternative.

Many of the most popular freemium products have a price point that is low enough that large numbers of people can easily justify the price, if they actually use the product.