Product variant attribute not changing price in 1.6

Anyone else having an issue with product variant attributes in 1.6 not changing prices in the shopping cart?
I have setup a product and one of its variants has an attribute. This attribute, if checked, should add $10 to the price of each variant purchased. However, when I do the math in the shopping cart, it does not add $10. It does show in the shopping cart that I checked the attribute and that it should be +$10.

http://solidealtires.com/products/7-10-x-165-tires-only.aspx
username   [email protected]
password 1234567

Example:
Product one is 10x16.5 Rubber Tire
Variant is Gripper
Attribute asks " Mount tire to rim?"

If you check Mount tire to rim radio box, it should add $10 to each tire purchased. It doesn't currently add the $10, is this a NopCom 1.6 bug or have I not checked some esoteric "allow attribute price changes" value in "All Settings"?

Any help is much appreciated.

By the way, what I would really want instead of making this $10 fee a product variant attribute would be to make it a "conditional" shopping cart checkout attribute.  Basically I would need some sort of logic in the backend that said "if a customer buys X and Y together, have conditional checkout attribute Z appear in shopping cart and make required"

Thats probably asking too much though  ;P

OK, I did find and check the dynamic pricing option, and it does dynamically change the price on the product page, but when you go to the shopping cart it goes back to the original price.

Anyone having this issue?

My other site is getting a nopcom store as well, and I'd like to make sure this is fixed.
http://www.tracksandtires.com