Not that low if you ask me (I can even say that I'm surprised with the bonus), I am at Gold rank now (wager $100k) and the total bonus I have received so far is more than $400 (more than 50% comes from the level up + tier up).
Almost 70% of it has come from the level up bonus. I only got $25 from the level up bonus after reaching the silver rank. Then I decided to use their '
Tier Matching' option and become '
Jade II' rank user for this. And this is how my bonuses look after wagering $50k in total
[REMOVED IMAGE] 
Do you know what is the most disappointing part here? The daily, weekly and monthly bonus rate. Those bonus rates are 3% of the house edge. If we combine those 3 bonuses, then it becomes 12% of the house edge. They don't include the lossback in any of those bonuses. On other casinos, the daily, weekly or monthly bonus is individually
5% to 10% of the HE.