You do not need to spend five million dollars to get the 5k off. The ratio is 10,000 points = 100 dollars off maximum of 5000 = 500,000 points. Standard card is two dollars for one point. Which is 1 million dollars. Which still sounds like alot of money , but you need to consider you can accumulate points over a period of years.
You can also upgrade it to the 50 dollar annual fee card which you get even point for dollar which cuts that in half.
So the initial math was off by 500%. More if you spend the 50 bucks to upgrade it. Keep in mind with this and all rewards cards, this is money you are spending anyways that you get STUFF for. I don't know where the notion comes from that you just kinda give away all this money to the card company to redeem a small rebate and have nothing to show for it. Anyone with a family of 3 or more can attest how quickly you can spend money just feeding everyone. Many cards have better conversion %'s but the points expire more rapidly. It's not going to be for everyone, but you can benefit from using it.