Just a heads-up to avoid over-spending.
Amazon Video has begun automatically deducting any available credits for no-rush shipping from the video's listed, visible price.
In other words, if you have $5 in credit, and you see a price of $5, the actual price is $10, and it will both eat your credits and
charge you five bucks in cash. You'll see lots of $0 pricing for rentals, too. Don't take those as freebies, they're also reflecting available no-rush shipping credits.
You can see actual pricing by opening the pages in another browser that's not logged-in to Amazon.
This is a confusing mess, and I hope Amazon realizes it and reverts to showing actual pricing.