I use an app called Price Cruncher. It's useful especially when you're buying things in bulk because it automatically calculates price by unit (even if the unit differs from entry to entry). You can keep track of where you bought it from and see a price history. It exports the data into CSV too.

Ive been using price cruncher on Android for the last few weeks (https://play.google.com/store/apps/details?id=ca.brainservice.pricecruncher.free)

It doesn't have a barcode scanner, but it does let you log the price per unit and compare by product or store. I am finding that the more I use the app, the less I need it though, as I'm quickly learning what "good" prices for things are.

Not OP but I did recently discover this app called Price Cruncher that works pretty well for this kind of thing. You can add items and track prices across different stores/brands/dates and also note if the item is on sale or not. Very customizable although it does require a bit of work to input the data. You can also export to CSV (which can be converted into spreadsheet format). My major gripe with this app is that it has no computer equivalent so you have to do everything via app.

Ich habe, als ich noch Android verwendet habe, das hier benutzt:

https://play.google.com/store/apps/details?id=ca.brainservice.pricecruncher.free

Das ist nicht ganz, was du suchst, weil es eher zum vergleichen von Preisen aus verschiedenen Läden ist, aber gegebenenfalls ist das das langfristige Ziel?

Ich vermisse die App unter iOS :(

A note for those like me that are terrible at math/conversion - there are free apps for your phone that allow you to compare prices even if the measurements are different (e.g. ounces vs. grams or whatever). My favorite appears to have disappeared ("What's The Best Deal", I think it was called), Price Cruncher is what I ended up replacing it with.

IF YOU HAVE ANDROID, THERE IS AN APP!!

Price Cruncer is fan-freaking-tastic!! You can choose the stores, choose your units, and choose to present your list of items by either cheapest unit price or latest price.

There are screenshots on the app page but here are some of mine. I like to separate my paper products by ply. To view the price history, press and hold on an item then a screen will popup. I like to sort mine by best price, but you can choose to sort by most recent price, and by store.

Once you're back on the default item screen, once you tap on an item once, you get this which also has the best price on top. The only requirements are price of an item and the quantity, but I like to be as descriptive as possible so I can possibly duplicate it later (like marking if its a sale price or regular, marking the date, marking the store, marking if its a bulk purchase i.e. buy 4, get 1 free, etc). So once you want to compare to past data, you can input on the screen (here's an example) and press the 'Crunch' button to compare. Under results, it'll tell you if its more expensive, cheaper, or the same as the previous best price and you can choose to save the data for later by pressing save or just exiting the screen if you don't want to save.

This is just a very rudimentary explanation but my goodness, this is a damn fine app. My only problem is that it has ads (you can pay to remove them), there's no web option, and its kinda ugly (lol). YOU CAN ALSO EXPORT YOUR DATA FOR FREE THROUGH A CSV FILE (I like to backup every so often to google drive). But, overall, this is a fantastic app!!

TLDR; Price Cruncher is pretty much the best app for a virtual price book although it doesn't scan barcodes. The main negatives are ads, ugliness, and work to input data. It's free though, so check it out :)

I use Price Cruncher on Android.

https://play.google.com/store/apps/details?id=ca.brainservice.pricecruncher.free

Android users, check out PriceCruncher! Great app for comparing per-unit costs across multiple stores.