Costco.com[costco.com] has Ring Alarm Wireless 10-piece Security Kit for $239.99 with free shipping for Costco Wholesale members. (When this thread was initially posted, it was for a pre-order for shipping on 07/13/2018.)
Alternatively, select Costco Wholesale stores also have this product in stock as of 07/11/2018 for the same price. It is recommended you call to ask for availability prior to visiting the store. (store locator[costco.com])
The kit includes:
6 Contact Sensors
Price Research and Other Kits
BestBuy.com[bestbuy.com] has a $299.99 package that consists of 2x keypads; 2x motion detectors; 3x contact sensors; base station; extender; and solar security sign. (I compared the BestBuy.com to Costco deal here.)
As of 07/04/2018, the solar security sign may no longer be available.
24/7 professional monitoring for $10 per month or $100 per year (sold separately)
Author's note: This is significantly less expensive than other monitoring services, and that's the biggest benefit of this system. For a consolidated look at multiple monitoring services, see my post below.
No contracts and no cancellation fees
No professional installation required
Works with Ring Video Doorbells and Cameras
Author's note: Some regions, counties, and cities require registering for a permit to have home alarm security systems. Please check with your local government agency.