The PRO EDU PRO Plan's prices will remain constant if the membership does not lapse.
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PRO EDU PRO PLAN MEMBERSHIP
Will My PRO Plan Price Increase When It Renews?
All PRO PLAN members are locked into the rate/price they signed up at, and this cost will not increase for them as long as they are active members.
If the membership is canceled, this will create a break in the service. If the membership is then renewed at a future date, the price may increase to the current pricing.
Check current pricing at https://proedu.com/collections/pro-plan-membership-options-pricing