Sure, that's true as far as it goes, but it gets a little strained when you see the similarly-priced competition. Pricing isn't a function of absolute utility and value, it's also a function of economic environment.

Take Apple display adapter dongles. Do I get a ton of use out of them? Do they make my MacBook better? Sure, but $30 is still a cruel fucking joke.

My wine key feels great in my hand, never breaks, and has given me loads of value and joy over the last decade but I would still be a fool to pay more than $5 for it.

I've carried a plastic Japanese fan in my bag for more than ten years that has saved my sweaty ass in many social circumstances, and is indispensable for my personal well-being between July and September; it's covered in ads and I got it for zero yen and I wouldn't have paid much more than that for it.

All that said, the correct price of a thing is whatever people will pay for it, and 37signals has certainly demonstrated an uncanny ability to find their market.