I have been wondering about the way the contestants address the people they have to pitch to. I'm not in the UK and English is not my first language, but I cringe whenever they come in and greet the people with 'you guys'.

I think Jim was the only one not doing it.

Is it the common thing to do?

It is extremely common, but I'm not sure it's the done thing in a situation like a pitch. Seems too informal.

I wouldn't expect that as a greeting in the circumstances mentioned but if they were referring to the group later - e.g. "If you guys like the product", it would not seem too informal to me. Personally I would omit the 'guys'.