Hello,
When a customer buy a subscription product, the cost is what is configured in the product.
Regarding the type of subscription link, the product can "create", "renew", "renew or create", "creation then renewal" a subscription.
It means that you can have different products (and prices) for the creation of a new subscription and its renewal.
When you're using "renew or create"/"creation then renewal", the product can be used for recurring payments.
The upgrade is also an HikaShop product with a subscription type.
It allows to "upgrade" from a plan to another ; the price is set by the product itself.
Once a subscription is upgraded, its renewal is based on the products which can perform that action (renew / renew or create).
So it's really based on how you configured your products and their prices.
Upgrades and Renewals are proposed to the customer in his customer dashboard, so he can select the subscription he wants to renew.
The product pages are for new subscriptions, so the customer do not have extra interfaces to select the subscription (to renew or upgrade) ; we made some tests but it was too confusing for users.
Regards,