i understand the point of the tutorial is that you set a base price in the products table.
then in the product options table, you set the amount the price should increase by for each size.
for example, the base price could be:
if you want the options sizes to priced as:
small = $8.00
medium = $11.50
Large = $12.00
X-Large = $14.50
in the product options table, the price increment column would be set as:
small = 0 (+ 8 = 8)
medium = 3.50 (+ 8 = 11.50)
Large = 4 (+ 8 = 12)
X-Large = 6.50 (+ 8 = 14.50)
those are just examples so you can get the idea.