I don't think so. Different casinos have different approaches to marketing. Maybe Duelbits spending more here as they considered bitcointalk campaign as a profitable marketing campaign. Nevertheless, the money you have mentioned here isn't a big some considering how much a casino earns & obviously, it's a business with a huge amount of money in hand. Besides, it's possible as well that they aren't new in the industry. If you look at Livecasino.io, they are spending a lot since the beginning. How? because they are a sister site of sportsbet & bitcasino.