Amazon gives non-Prime members free shipping at $35 or more of eligible items. Instead of simply letting users get the product with free shipping, they’ve added a discount that prices it exactly one cent below the $35 limit, while only subsidizing the price with $3.38, which is about half of what they’ll then charge you for shipping.
You get more protection from your credit card company than Paypal. If your item doesn’t arrive or doesn’t work, you can file a chargeback and get a full refund. It’s worked for me every time I tried it (Visa card from Royal Credit Union).