You're right in a sense, decisions based on cost alone are usually prone to dissapointment. Best "value" is the key.
Choosing something that is "the cheapest" that still attains a recognized international standard is perfectly valid.
For example, a dust mask with a BSI kite mark bought from a pound shop is just as good for the purpose as one bought for £3.99 from a large DIY store with large orange lettering.
Buying comparable product without recognized standards though is very difficult. That's why standards were created.
Large supermarkets can sell items cheap because they have a high turnover of stock. In the same way, the largest flying training facility also has economy of scale.