[sdab]

If a user realized that the "cost" of viewing the image was free, wouldn't the user disregard the cost on future instances of the experiment?

Did the experiment limit a user's participation to one time? Otherwise, the results might be skewed and the benefits exaggerated.

[ankitjain_hn]

Yes, it limited the participation to one time. We don't show "locked" images, after doing unlocking. Most visitors are expected to be one-time visitors, finding the recipe via Google Search. Even if they re-visit, IMHO, it is measured risk to take in order to get actionable data for taking further decisions on shaping this feature.