How Diamants de Paris lowered CAC by 14% while restoring Meta signals

Diamants de Paris had reduced its Meta investment after acquisition performance weakened in the post-iOS 14 environment. The team wanted to regain enough measurement coverage to scale with more confidence.

The challenge

The account’s customer journey was only partially visible to Meta. That made it harder to evaluate which ads were producing valuable outcomes and limited the feedback available for delivery optimization.

What changed

Diamants de Paris connected Bily’s Edge Pixel to send customer events through a server-side path. One month later, the recovered record reports 65% more event data reaching the Meta pixel, along with stronger Event Match Quality.

Meta Events Manager before Bily.

Meta Events Manager one month after Bily was connected.

The result after 15 days

The original account notes say the ads kept running without campaign changes and that the last campaign edit had been made seven months earlier. During the first 15 days with Bily, CPC fell 22% and CAC fell 14%.

How to read the result

The timing supports a useful before-and-after comparison: signal coverage improved, and acquisition costs moved in the same direction while the campaign setup was reportedly unchanged. The record does not establish a randomized control, however, so tracking should not be treated as the only possible influence.

Auction conditions, creative, offer, audience, and demand can also change results. These figures describe the brand’s 2023 account and are not a guarantee of future performance.

Next steps

The next measurement should keep the attribution window, campaign structure, and comparison dates explicit. Reconcile Meta-reported conversions with paid Shopify orders, document every material account change, and track CAC alongside contribution margin. Increase spend only if signal coverage remains stable and the paid-order economics confirm the platform trend.