At least here in Norway, though similar in many other countries that I know, it's not entirely bogus.
Typically there are real costs involved with submitting a customs declaration, especially if it requires actual people looking at the invoice and filling out the customs declaration based on it. An order from JCLPCB or similar would typically fall in that category.
Then there's the duties. Either they hold the goods until you've paid, in which case they need storage space and bookkeeping, along with inspections from customs every so often. Or they just pay up front and bill you after the fact. In either case there are real costs involved.
That said they're certainly not a charity, and I do think they exploit a bit the fact that often the importer doesn't have much of a say or knowledge in picking the shipping company. Perhaps the seller only deals with UPS for example.