Chart View
The historic price of an item is important in assesing its value, if you were to have a chart of previous sale prices of an item it would be easier to asseses when you are paying a premium because of shortage/seasonal demand. Aditionaly, it would be easier to see inflation.

Average Price
On general items such as pasta, having a single price for a bag of 500g of pasta would be a very useful metric to judge the value of a specifc item. This would be especially useful if you were using the app whilst shopping as it is unlikey that a user would be prepeared to walk to another shop, however knowing the going rate for pasta will allow them to make more informed descions.

In terms of calulcating the price, a simple average over comparable items would suffice. I would also argure that more techinchals would also be useful for shoppers, such as volatility metrics or an items beta with respect to infaltion would be very useful figures for shoppers to know and to understand.