Planet Coaster
Pricing:
Was: $64.95
Now: $3.24
Steam Reviews
SteamDB
Bargain History
Not sure if this is the historical lowest price, although i believe it may be after looking up SteamDB, at least directly through Steam.
For me personally well worth it, very reminiscent of the old Roller Coaster Tycoon games I grew up with :)
IsThereAnyDeal is the best place to check PC games for price history. According to them this is the ATL. They also track bundles and this has appeared in one, Humble Choice March 2020.