Price promotions (discounts)

[raphodn]

This discussion will help gather information on price promotions.
And find a quick way to better manage them in the backend & frontend.

List of promotion types

Name	Example	Details	Status
Discount on a product			Currently implemented, with price, price_is_discounted & price_without_discount
Discount on a product because expiring soon
Buy X get Y free (BOGO)	Buy 2 get 1 free
Discount above X quantity	Buy 1 get the 2nd at 50%
Pick it yourself	- 5% discount on books - Discount if picked at the farm

Related issues

• Manage discounted prices #76 (current implementation)
• Price: Bulk pricing promotions #495
• Add discount "restrictions" checkbox open-prices-frontend#537
• Discounted Price and Full Price should be allowed to be the same open-prices-frontend#840
• New DLC/DLUO field #472

[serpico]

in the case of #840 I was also hoping/trying to think of a way to warn user for this specific case, it says discount on the price tag but the price is the same than it was for the last X weeks, so there's no real discount ( I admit I don't know if it's forbidden, to advertise a discount while nothing changed ). I thought about a special color on the graph for that the price points of discounted price ( since the graph will be flat we could see the discount is bogus - and the opposite is true ) ; we could also use some stat i.e mean/average price for the last month, last 2 months in order to give an indication of the extent of the discount.

[serpico]

funny thing, when there's 2 prices ( normal price and discounted price ) for the same day/same location as for https://prices.openfoodfacts.org/products/3564706596788?display=chart it's plotted on the graph as a single price point which seems to be the average of the two

see also 302

[raphodn]

indeed, currently the chart's Y axis does a "mean aggregation" of the prices for a given day
here : https://github.com/openfoodfacts/open-prices-frontend/blob/646ca0ff9f98d3e2eb84cb281097702402aab78f/src/components/PriceChart.vue#L48

[tradmangh]

funny thing, when there's 2 prices ( normal price and discounted price ) for the same day/same location it's plotted on the graph as a single price point which seems to be the average of the two

not funny at all ;) and it shows that for complex data there is no such thing as a "simple chart" ;)

different prices ...
same location: not ok, data quality issue
different location, same store chain: probably not ok, depends
different location & store chain: should be visualized as Min/Max/Avg for each datapoint, which makes more sense
...

[tradmangh]

Discount on a product because expiring soon

"to good to go" discounts are a whole different story, because they only apply to specific physical product items. While that information might be interesting for certain parties, for useful stats it would need a huge amount of datapoints and regular data capture. Also very rare and short lived.

Discount above quantity x Buy 1 get the 2nd at 50%

For food products the most common case is a bulk discount, x% discount on all items of the same if you buy more than x

Other variations for discounts:

• "Member_only" which are often combined with BOGO
• "x% on the most/least expensive item" but I have not seen it with food products so far

[serpico]

to add to the recap table :

Some shop=farm offer a "pick it yourself" discount, you can either buy already harvested produce in a display manned by an attendant/cashier but you can also pick/harvest the produce yourself in the fields and they're discounted. Prices for picking yourself are displayed on a big whiteboard/chalkboard.

Those cases could also be interesting candidates for crowdsourcing the extraction of prices from pictures ( #523 ) as you need 3 to 4 pictures to catch the whole board and it's evolving depending on the harvest season - those kind of shops generally have a limited presence online and from a customer's perspective you can't really plan on buying "to harvest" and generally have to wait till you're in front of the board to know current prices and availability.

That's one of the cases where I feel open prices could be a killer app - but a special tag as envisioned by @TTalex in #523 might be necessary to ease collaboration for an informal group of customers of the same shop, sharing the workload and keeping the prices updated - it could work great for a projet du mois-like ( openfoodfacts/open-prices-frontend#934 again brought up by @TTalex ) using overpass turbo query https://overpass-turbo.eu/s/1Te8. to identify those shops...

Different cases of prices I've seen in those shops :

• Price per unit or kg at the display - depending on produce there's sometimes a discount depending on the amount.
• Discounted prices at the display for légumes moches , sold per unit or per kg.
• Prepackaged/preweighted amount ( net of 5/10kg for potatoes, onions ).
• Price per unit or kg if the customer pick the produce herself/himself in the field, usually it's a flat price per kg/unit regardless if you take an overflowing wheelbarrow of produce or not....
• Discount for big amount to be picked by the customer ( end of season for tomatoes, I've seen discount if the customer pick and buy 10 kg in one go ).

I feel you would need up to as many pictures as there's cases, in a recent example for yellow onions :

• 1 picture with prices at the display for onions at the display ( 2 different prices whether it's per 1 kg or per 2 kg ).
• 1 picture with price for a net of 10 kg.
• no price/no mention of onions for pick yourself as the harvest season is over.

edit : added example's pictures for potatoes