We live in a VERY high food-cost area, so groceries are a part of the budget that we are constantly fighting with. I have been unable to find a good app out there for tracking grocery prices that had all the features I wanted: free, cloud-based, with no ads, and tracks the price, unit price, store, date purchased, and whether or not I bought it on sale. I want to be able to quickly see if today's price on Item X is more or less than what I've paid before, and to be able to track prices over time.
So, using MementoDatabase, I built a very simple relational database app that does all of those things! I have no experience designing apps, but I do understand relational databases. The database isn't very pretty, but it works smoothly. It has two tables, one for items and one for purchase events, and I can add to both tables at once without duplicating items. I can also view all the past prices I've paid in chronological order to track trends.
Unfortunately I don't think I can share the empty configured db, but if you are looking for something similar and understand how tables work, you should go for it. Memento is pretty easy to use, and has a library of available preconfigured databases that one could modify, by the way. We are looking forward to seeing if this new tool helps us keep our food budget in a mustachian range.