It’s not entirely obvious from the description, but the main difference is (I believe) that the cheap keys can only do FIDO 2-factor authentication whereas the

It’s not entirely obvious from the description, but the main difference is (I believe) that the cheap keys can only do FIDO 2-factor authentication whereas the expensive ones have secure storage so you do things like putting your pgp private keys on them. If all you want is true 2-factor authentication for Gmail / Facebook / Github etc then the cheap keys are exactly what you need.