I am not really a big bettor but I want to feel that I am belong to the casino and I'm still welcomed in their promotions and campaign, usually the promotions are only for whales or big bettors and some small bettors we're not that interested to the big challenges or promotions as it would only fit to whales. I think having two challenges 1 for whales and 1 for the small bettors would be much better.
Or make a challenge where everyone can participate for example a challenge to reach $1000 with only $10 as starting as most of the bettors including small bettors would be able to participate.
I think what you are talking about is more likely related to Bonuses, where some bonuses require the user to spend or wager a ton of money to be eligible to claim the bonus, and we all know that in such situation, any user who can not afford the required wager amount would likely miss the bonus, we now can say of a truth, that that program was meant for whales only.
But on the other hand, we are talking about challenges here, Challenges, to my own understanding are more accommodating, since it mostly would require a certain amount of money join, and that amount must not be much, if not, a lot of pleb gamblers wont join, and when a challenge does not have many participants, it is always not interesting in most cases.
This is just my opinion though.