This product is priced at $10.00
It is marked Price by Attributes.
The attributes are priced using the Price Factor and Price Factor Offset.
The actual Product Price is used just to compute the Price Factor.
Red is $10 ($0)
Yellow is $20 ($10)
Green is $30 ($20)
The Price Factor Offset is set to 1 to take out the price of the Product Price then make the total price the price factor * $10 - price factor offset * $10 for the attributes.