@Janha I’m assuming you are a PS4 player.
The text at the bottom of your flash offer is inaccurate as PS4 does not allow currency such as gems to be reduced in price. PS4 players receive the equivalent value of gem keys instead of the gems that PC/Mobile players get. The offer on PC/Mobile does not include gem keys
This graphic issue was supposed to be resolved but obviously that’s not the case this weekend.
You should find this thread helpful. [Addressed] Flash Offer 31/01l/20 Vault Offer - #19 by Ghaleon