Carp, Maybe the answer is here:

ProCare is only available for separate purchase at a Apple Retail Store for up to three Apple computers owned and registered in your name. Customers are limited to one ProCare membership per year. ProCare will be valid for one year from the date of purchase. If ProCare is purchased by a minor (under 18) or on a minorís behalf, an adult must be present to agree to these Terms and Conditions. An adult must be present with a minor under the age of 14 for the duration of the in-store services. ProCare services are valid only at Apple Retail Store locations and cannot be used for service requests made through the online Apple Store, Apple Telesales (800-MY-APPLE), or any Apple reseller or service provider. Presentation of your ProCare card and another form of identification may be required before ProCare services are provided. ProCare services are not transferable. Apple reserves the right to refuse, limit, or cancel any ProCare service and/or membership if a customer has displayed unreasonable behavior; is deemed to be violent, abusive or disruptive; or has otherwise breached these Terms and Conditions.


It doesn't specifically say what the price for 1 or for 3 Macs would be. Seems to me, they mean one price for 3 Macs.