The sale says Up to 50% bonus.
The bonuses have increased by tier, you receive the maximum bonus if you buy the higher amounts.
Normally the bonus is much smaller for lower tiers; 3%, 5% etc.
You people need to learn to read, seriously. You should know how sales work by now. They're meant to catch your eye, but a smart shopper always knows to look at all sales a little more closely. Let it be a life lesson to you.