It’s literally not double the price. Office 365 is $5-15 depending on edition (Business Essentials, Business, and Business Premier) and if you do an annual commitment. That’s the same price range as GSuite which is $5 to $25 depending on version (Basic, Business, Enterprise).
Sources:
https://products.office.com/en-us/business/office-365-busine...
https://products.office.com/en-us/business/office-365-busine...
https://products.office.com/en-us/business/office-365-busine...
https://gsuite.google.com/pricing.html