summer sale

So, I know the Summer Sale is going on in the shop, and I'm really loving it. I've also been using ads to work up coupon codes to use, but I really need to know the deadline to when I should spend them before the sale ends. Now, I know it's a "Summer" Sale, so I'd expect it to continue into at...

Okay so I am an Overlord which I bought for $40 a couple days ago without the sale. Now I see that the Hero rank is $20 from Overlord to Hero. But my friend says Hero is only $50 for them which would make it $10 less for them compared to me. I don't get it. They get to pay $50 for Hero perks...