Warning: in general, the older the game is, the greater the discounts offered, but in some cases, a very old game actually increases in price after a while. This is specially true on Steam because a game can have a different price for each region, and conversion rates from one region's currency to another can change all the time, e.g. Call of Duty: Modern Warfare 2 (2009) more than doubled its price in Brazil from R$39.99 to R$91.90 in October 2023 (the U.S. Dollar price stayed the same). Additionally, some old AAA games sometimes simply stop being sold on Steam at all, and are replaced with remastered "HD" versions with higher price and less discount, e.g. The Elder Scrolls V: Skyrim can't be found if you search for it on Steam, although it can still be purchased if you can find its page from Google, only the Special Edition can be found by searching for it on Steam.
To view the highest discount of a game on Steam, follow the following steps:
1: go to SteamDB's website via the URL:
Note: SteamDB isn't officially affiliated with Steam, it just has a simliar name.
2: in the search box at the top, type the name of the game you're interested in purchasing. A dropdown list will appear showing titles of games that match your query.
Hollow Knight" in SteamDB's search box.3: click on the game you want to purchase. You'll go to that game's page on SteamDB, where you'll see a list of its current price in various currencies in a table.
4: click on the name of your currency, e.g. U.S. Dollar or Brazilian Real. This will display a graph of its price history.
5: hover your mouse cursor over the graph to see the price at specific points in time.
In general, the discounts of a game increase over time. Some games have discounts of around 90%, but most games will never go on sale for that low no matter how much you wait. There are cases of games that increase their discount until the limit, and then every sale you get the same discount. But there are also games that go on sale with varying amounts of discount even after they have been on the market for a long time. In either case, it makes sense to check just to be sure.
Observation: if I'm not misremembering it, in the past, this graph used to span years, but it seems currently the "Max" it will show is only a little over a year. A message under the graph says the data displayed publicly is limited, and you need to login (i.e. create an account) to view more data. In most cases this won't be necessary. You can still view more than a whole year of data without logging in, which means you can see the price of a game during the last Christmas Sale (Winter Sale), Summer Sale, Halloween Sale, etc. If a game hasn't gone to 50% discount during these sales in a whole year, it's unlikely that it has had greater discount before that, or that it will have that same greater discount after that.