Blue Iris is a video management system and can be purchased for a base price (currently $69.95). However, updates to Blue Iris (not mandatory) to later versions must be purchased for an additional fee.
Sentry Smart Alerts is a service provided for the Blue Iris platform to help filter notifications using Artifical Intelligence. You pay for Smart Alerts like a subscription, meaning monthly or annually. Smart Alerts can be used on most versions of Blue Iris meaning you don’t have to repurchase Blue Iris in order to continue to use Smart Alerts