Why did I have to pay for "promotional" gift card?

No scam. Apple clearly explains this is what is happening in their promotion information.

The offer is for a $150 gift card with eligible purchases. Nowhere does it say you will get a discount on the product you are buying only.

If you did not want a gift card then why apply for an offer that clearly states it will give you a gift card?

You get a discount on the Product you buy and are charged for $150 gift card. Why they do it this way, only they know, we cannot explain it nor can we argue about Apple's policies here.

Next time read the information carefully so you know what you are getting into before hand.

Link-> Back to School - Education Discounts - Education - Apple

 3. Qualified Purchasers receive an Apple Gift Card when they purchase an eligible Mac or iPad at a Qualifying Location. Only one Apple Gift Card per eligible Mac or iPad per Qualified Purchaser. Offer subject to availability. While supplies last. Qualified Purchasers shall receive a discount equal to the value of the Apple Gift Card off the price of the eligible Mac or iPad, but will be charged for all items in their cart, including the Apple Gift Card.

Though it is not a scam per sae, it absolutely feels like false advertising. A gift implies something given. Can you imagine giving someone a gift for their birthday that they have to pay for?

Though it states in the fine print that the total sum equals the same amount as the retail value of the device, the promotion feels manipulative and misleading for sure. Not to mention the promotion bar says “$150 towards college”. In what way is paying my own money onto a gift card helpful towards my education?

I’m not sure I would’ve read that find print and understood it either way. Because it truly makes no sense. I’m glad I’m not alone in feeling lead on and enticed to “hurry up and purchase”.

Again no. They deduct $150 from the price of the laptop and then charge you that same amount for the gift card. You aren't paying for the gift card an extra $150.

You are getting $150 you did not pay for anyway.

If the computer is $300, you pay only $150 for it, and $150 for the gift card. At the end of the day you get $450 dollars worth and you only paid $300. Yes, it's a very convoluted way of doing it, but it is what it is. And you are getting the $150 as promised and are not paying anything extra for it.