Just purchased a FireStick TV 4K for $24.99 plus tax and at checkout have this:
Congratulations. Your purchase qualifies you for $45 Sling TV credit ($15 credit per month for 3 months). Offer eligible to new Sling subscribers only. Your promotional code will arrive within 7 days after your device ships to the email account you have registered to your Amazon.com account.
I think they have the same offer last Prime day.
On top of this, there is a 15% credit/reward if you use your Amazon prime card.