In order to update your prices, create new Prices in Stripe for each that need updating and archive old Prices. You can only edit a Price's price if it has not been used to create a subscription.
Create new Price
Go to the Stripe dashboard and select a Product that is part of your service. Click "Add another price" to create a new plan at the price you want.
Create another price
Archive old Price
Then, go back to the product and archive the old price by clicking "..." and "Archive price".
Your Billing Pages will automatically update for the new pricing and customers already subscribed will remain on their current pricing. They will automatically be grandfathered in and only change their price if they change their plan to the new price or cancel and resubscribe. This process will keep you from generating unnecessary products in Stripe and is easy to maintain.