I would be very wary of such offers, as they you don't get something for nothing.
There is a price to pay as they would have to get the licenses in the first place, even if they did a bulk buy as an avast distributor there would be a cost. Whilst they might do this on the basis of picking up a customer long term, then they could cover the cost.
But I would still be very wary. Checking if they were avast distributors, does the site have any google history of sharp practices, hacked/cracked software, etc. etc.