A lot of misinformation here.
The best sale we have had was the 40% more for the 4500 cash vault. This was only offered on cyber monday and new years. other than that the most the vault has been on sale a couple of times with a measly 10% bonus.
The 500 cash chest had a 50% bonus on cyber monday and new years. It also had the 50% bonus a couple of time before that as well.
So the sale on the chest of coins isn’t great. But technically the vault say is better that the other times its randomly been on sale. Just not as good as the haoliday sales which tbh is expected.
edit; meant this as a general reply. what zendrexin said was accurate