Costco Wholesale [costco.com] has for its Members: Philips Sonicare ProtectiveClean 5000 Gum Care Edition Rechargeable Toothbrush , 2-pack for $69.99. Shipping is free.
Note: $30 manufacturer’s savings is valid 1/20/20 through 2/9/20. While supplies last. Limit 2 per member.
I am not sure what is the difference between 5000 and 5100 but if any, looks minimal. At this point, 5100 is for $69.00 for a single unit while 5000 at Costco is for 2-pack for the same price.