Problems with option in shopping cart

Hi Chris,
    Leave the products price at $4  but REDUCE each option price by $4 - so the totals are correct.  I'd advise adding some wording to make it clear that  this is the additional cost for the larger size / number of bottles.
For example make the 5oz something like 
"5oz (Standard Size)"   and price the "option" at $0 as this is the price of that product anyway.  The option prices are additional costs.

Really these are separate products, not options on the base product, which is why it doesn't quite "hang together", but I can see why you have done it this way and careful clear wording should suffice to make customers comfortable with what's in their cart.
If not, then the BTO version does this very smoothly, or just have separate products for each variation - either route would also give you separate SKU's etc for each version.

Hi Katharina,
     That's a good point & a good approach. How did you hide the zero price of the product without any option set? Did it happen automatically or did you have to make a change?

The old version used to show $0, but the new one doesn't.  Sure you have to click on the option to see a price, but that is a no brainer.  I fell it simplifies the price issue.  It still shows the word "add".  I should find that part and fix it.  It's probably somewhere in the languages.asp file.
Katharina

just put the word "cost" instead of "add" and voila...  I haven't changed the add yet, since nobody seemed to be confused about it. 
Katharina