Shopify Plus plans come with up to 10 stores at the base $2,000/month fee. However, the fee is dependent on actual revenue based on the 0.25% platform fee. Additional stores require 3 out of 4 policy guidelines to be met (Same look and feel, same product catalog, same URL structure, same point of contact). International versions of the site, wholesale versions, and sub-brand segments of the primary business meet the guidelines for up to 10 stores on a single plan and $250/month for each additional beyond 10. If you utilize Shopify's locations features then there is a 20 location cap for each domain and store on the platform.