Since the longest time, Apple only sold Thunderbolt 3 cables from Belkin at lengths of 50cm ($29.95) and 2m ($69.95). Finally, though, Apple is now providing a first-party cable at 80cm long for the price of $39. All three cables are on sale at the Apple Store online right now.
Of course, other options are available elsewhere. But with the fact that Apple has so poorly-equipped its latest MacBook Pro models with two USB-C ports and no legacy connections, you’d wish that Apple put its name out on some accessories for the professional types that needed all of the I/O.