Shopify Buy with Prime A/B Test: Why Amazon's Checkout Button Lowered Revenue per Visitor by 30.8%

TL;DR

A European car diagnostics brand sells an OBD2 scanner alongside a paid app that unlocks hidden car features, advanced diagnostics and service tools.

The product page is where this sale is decided. Shoppers arrive with questions about compatibility and the subscription, and most leave without adding to cart.

As part of our Shopify A/B testing programme for the store, we added Amazon's Buy with Prime button to the main product pages. It lowered revenue per visitor by 30.8%, the largest loss in the brand's 2026 programme.

The challenge: low trust at the moment of decision

In our June 2026 audit, 98.9% of about 720,000 visitors never added to cart, while 76.9% of those who reached checkout completed it. The sale was being lost on the product page, not at checkout.

A familiar name like Amazon looked like a way to make a first order feel safer.

The research: what was already breaking trust

In our Shopify CRO research, a walkthrough of the product page, read together with analytics and customer surveys and reviews, showed where trust was already breaking.

• ✓Price trust: the price shown at add-to-cart was about 17% higher than the advertised price, because a pre-selected extended warranty was added by default.
• ✓Subscription opacity: 36 negative signals described unclear subscription terms or hidden fees.
• ✓Compatibility doubt: 19 negative signals came from shoppers who couldn't confirm their car was supported before buying.

The hypothesis: borrow trust from a familiar checkout

If we add Amazon's Buy with Prime button to the product pages, shoppers will feel a first order is lower risk, increasing revenue per visitor.

The variation: a Buy with Prime button on the product pages

The variation added the Buy with Prime button to the main product pages. The test measured the combined effect of these changes and does not isolate any single element.

The results: -30.8% revenue per visitor in 16 days

We ran the test in Intelligems, comparing the original product pages with the variation.

Most of the loss came from conversion: 28.1% fewer visitors completed a purchase, and order value also fell.

What this test taught us about payment options

A second checkout path is a second decision.

A shopper on this product page is often still checking whether the device works on their car and what the subscription costs. Placing two ways to pay side by side asks them to choose a checkout before those questions are settled, and a familiar logo does not answer them.

Trust signals work when they answer the doubt a shopper has at that moment. Here the doubt was about compatibility and price, and the tests that addressed those, such as our subscription clarity test, performed better.

Find out what is stopping shoppers on your product pages

We plan, build and run A/B tests for Shopify stores, grounded in customer research rather than guesswork. Get in touch to find out what to test next.