This power bank currently has a deal under the promotion dropdown. Where you can apply the promotion for each of the power banks you buy. (But can only be used once).
1. Just hover over the applicable promotions, and it should be the first promotion listed.
It should read as Pay $63.99 for each RAVPower 26800mAh PD USB C 30W Portable Charger. Here's how (restrictions apply).
2. Click Apply Promotion.
3. The new price should be listed at checkout.