There have been posts for the weekly DWG & Xbox Spotlight sales. I haven't been able to find a thread for this as of this morning. It looks like this week's price for Forza Horizon 3 is fair. The Horizon 3 Standard Edition sale price is only valid for Gold members. If you don't have Gold you can still buy Deluxe or Ultimate at sale price. Forza Horizon 2 Ultimate was on sale in the previous week for $36.
Horizon 3 is Xbox Play Anywhere so if you have the digital edition you can play it on PC or Xbox.