how much need to pay for upgrade my plan?

hi
if i want get the developer subscription in joomlapolis, how much need to pay to upgrade my account?
now i have professional plan.
thank you...

To upgrade your account, you will just pay the difference between the Developer membership price and the current remaining value of your Professional membership, pro-rated to the remaining period of validity. Just click the upgrade button to see the corresponding price. Then just click the payment button or the cancel basket link, depending if you want to proceed or not.

As time passes, the pro-rating discount will automatically decrease, as the remaining value is calculated from the current time until the current expiration date divided by the total duration of professional plan.

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