The PowerStore is designed to handle options for products as unique products, so you are not doing anything wrong. When it comes to creating the scenario that you presented it is not something that is supported within PowerStore. This would require you to come up with logic to get this in place as well as make the necessary updates to the code.
One way you could do something like this is to have an extra options table that has prices for these options as well as the item that corresponds. With this table in place you could add to the admin back end to update this table and add to it.
For the front end you would need to have a recordset that is filtered on the item, you can have a select list with the available options listed. If you modify your cart to include columns for the options and other values you can create a calculation that can determine the price for the bood based on the price of the item, plus the option then do the multiplication for the pages.
Making the updates like this would require you to make use of eCart and DataAssist. There will also be some hand coding involved to get it the way you would like it.
