Look up specifically what Admob, Crashlytics, and Firebase analytics track.
That’s the thing about data collection: its a lot of money to store. How are they funding the operation unless turning you into the product?
Are you referring to data on users, or data on the products this app tracks? The app doesn't need to store user data beyond what is required for it to function. Even if it stored such data, each user will only take up kilobytes to maybe a few megabytes because it's just text data.
As for the data on the products, by far the largest files would be images. The rest is just text data.
Standard Google Cloud Storage is $0.20/GB per month. There's no need for this app to store 16k+ photos, so the actual storage costs are negligible.