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.
For an academic text on this subject with footnotes, I recommend Chokepoint Capitalism (2022) by Rebecca Giblin and Cory Doctorow. It calls what you describe “moat buulding” and an “anti-competitive flywheel”.