Probably they will not disclose to public this kind of information especially the amount of there profit they get on there business. Let's just be happy that they are giving back there a portion of there profit to there players in the form of big time promotion and signature campaign payments like what you are receiving in daily basis. The duelbits promotions is very straight forward especially there cashback and free spin promotio on some particular sportsbet. You will get directly the reward straight to the casino balance without any bullshit requirements. This generousity reflects how big they are having profit on this industry.
Not only Duelbits, but I also don't think any platform will reveal this information until they have a chance to sell their share percentage. I don't think they only giving back a portion of their profit. It's a part of their business and promotion strategy. Every casino/platform has its own promotion strategy according to budget. So, They know what they should do or what not to do.