Yeah, these balloons that can hold small car to school bus sized payloads are not like a commercially available thing. It seems like they'd require truckloads of helium, which is a hard gas to store and not always available in massive quantities (seems like it should be prioritized for keeping MRI scanners cool instead of balloons). The balloons are probably really hard to produce, not made in great numbers, and require specialized equipment and processes to launch without puncturing. Not quite an airplane's cost but this isn't the send-a-gopro-to-100,000ft type of trick that relied entirely on products available to consumers.
It's also possible whomever is running this operation doesn't care about their staff at all and they just use hydrogen.
