Care plan pricing is per site — and a subdomain (like shop.yoursite.com or members.yoursite.com) counts as a separate site if it runs its own WordPress install.
It might live under your main domain, but maintenance-wise it’s a whole other beast with its own plugins, settings, and potential chaos. So yep — it needs its own plan too.
If it’s something super basic or low-maintenance, I’ll take a look and can quote accordingly. But anything with its own setup gets its own support.