That makes sense... I guess you should add it to the ProductOptions table... another solution would be to just have multiple Small, Medium, and Large entries so that each could have its own unique addPrice... really either way would work.
There are often several database designs that will work depending on the front and back end you use to access it. That is one of the most difficult challenges we have at webassist is that a lot of the complexity is in the database design and writing the proper queries... and we haven't figured out a way to help much with that since there are so many possible applications and scenarios that exist.
I would probably add them to the products table and add an accessoryParent field which is the ID of the product for this accessory rather than just a (0/1) field. That way I can filter out products that have a value in this field for the catelog and filter using the productID to get the related accessories using the same field.
