I do not mean that you should have monogramming as a product but instead you should have option groups for each of the various monogramming options. So instead of having a monogramming option with sub options you will just have the various monogramming options and if a user choses any one of them it will have the higher price.
You could add it as another item with it's own set of options if you think this would be easier to implement or if it would be more clear to the end user. If I were you I would go for one of these two methods as just having the info in a description would not help to make the process automated.