I followed your instructions however the price is not added to cart correctly and i'm not sure where I may have gone wrong.
I did a test for rsPriceLookup where variables recordID (I.E. url parameter or Productid for a t shirt) is 48 and postVariable is 5 i.e. x large option.
This brought up one row as planned with price.
Changed the variables' values back to -1 so that the values would be determine by customer selection.
I can see item is added to cart but not the price. On the previous setup just mentioned only that specific option price is added no matter what option I have selected when page is loaded.
SQL I have for Price is:
SELECT OptionPrice.Price, OptionPrice.SizeID, OptionPrice.ProductID
WHERE OptionPrice.ProductID = recordID AND OptionPrice.SizeID = postVariable