losthorizon: Hi Rudolf! A good resource for this is
Is There Any Deal. It checks all the major digital stores for the current prices, and also displays the lowest known price along and when it was active.
[url=https://isthereanydeal.com/#/page:game/price?plain=witcheriiiwildhuntgameofyearedition]In this case[/url], it appears the current price is indeed the cheapest it's ever been.
I only wish CDPR were being fair to those of us who bought the base game. The expansion pass i.e. the stuff that upgrades you from the base game to the GOTY only has 40% off. It does kind of feel like they are giving the middle finger to folks who supported the game earlier.
They either need to bump up the discount or drop the base price of the expansion pass to bring it into line with pricing for the GOTY otherwise it looks like they are pulling a Bethesda and 'fair play' with pricing is supposed to be something which is at the heart of GOG and their owner CDPR.