That kit is $40 on their site. Weird that it’s cheaper on Amazon in the first place.

No, Amazon does this on purpose. If you want to sell on Amazon, the search and recommendation algorithms will make your product hard to find unless you have Amazon fulfillment. But if you sign up for Amazon fulfillment, not only do you have to give Amazon a bigger cut of the price, you have to agree to never sell your product for less than Amazon does, even on your own website with your own fulfillment.

The FTC sued Amazon for this practice, and that case is progressing. But who knows if the Trump administration is going to maintain the lawsuit, or if the court will rule against Amazon.