Using an introductory rate for a subscription (ex. first two months are half off) encourages customers to purchase subscriptions.

To set this up, create a new subscription or edit an existing subscription (Memberships > Subscriptions & Packs) > scroll to Auto-renewal settings and toggle on 'This subscription auto-renews'.

Then toggle on 'Change price after certain number of renewals'

Lastly, set the number of renewals until the price changes > then set the new price customers will pay when after those renewals.