“I would not advise to use any index or any Benchmark because optimal price may depends on many parameters like age of your users platform type of product cultural specifics and it just must be tested.”

No Benchmark Replaces Testing — Optimal Price Depends on Your Demographics, Platform, and Product

Even Flo's own pricing ratios (the 'flow index') can't be safely transplanted to other apps, because the age distribution and iOS/Android split of Flo's users differs from, say, a fitness app targeting users over 45. Regional pricing is not a formula — it's a testing problem unique to each product's demographic fingerprint.