A: The calculation system expects the default attribute price to be part of the product cost and will only apply the difference between default and the option selected. Thus, if all are the same amount the price does not increase.  See Working with Attribute Group Options

Option 1: Create an attribute option "None" $0.00 and make it the default the attribute.

Option 2: Create an attribute option "Select Option" $0.00 and make it the default the attribute.

Option 3: If these are all the options, just added the .75 cent to the product cost and make attribute cost at $0.00.