Why am I seeing a different price than on the app store?
The Shopify app store isn't designed for a fluid, discussion-driven pricing policy; instead, it's designed for predefined, static pricing tiers. So, we use that tier structure in the app store to present the suggested prices available for each Shopify plan. This has the side-effect of having Shopify present the smallest suggested figure as the "starting at" price for Mechanic, which is not an accurate description of how any of this works. :)
The price you see in-app is a suggestion, per step #1 of our policy. To learn what to do with that figure, read the policy itself.