The Shopping Cart Content WebPart has a Hierarchy transformation, with the first level "Item transformation" being the product, the second level are any options attached to that product.
The Personlized Text should be a separate product option, so should be transformable in the 2nd level of that hierarchy transformation, and where you can add a note saying "by the way, this text is costing you a little more"
You can work with the main item transformation as well to maybe not show the total price (Unit price + Options) and instead just show the Unit Price so they can see the options separately.
If you don't have the transformation i mention, it's EcommerceSite.Transformations.CheckoutShoppingCart and can be found by adding a new Site and using the Web Template "Ecommerce Site", then the EcommerceSite page type with it's transformations will be imported.