You can do this by adding a new Pop up Skin and adjust the end user prices.

Add Pop up Skin

Login on MobileMoney with your account

Go to the menu 'My Account'

In the menu select 'Settings'

On the page select 'Pop up Skins'

Add a new one

Set the prices

Select 'Settings' in the menu for 'End User Price'

Select on top of this page the 'Pop up Skin' of the item you want to set the prices for.

After this you must make sure that the Javascript function mobilemoneysale will use the correct 'Pop up Skin'.

This way it is up to you how much you ask for a product (e.g. one of your Micropayments), while you can ask another price for the rest of your Micropayment products.