>  I'll see four or five prices
> from different suppliers, and the lowest might be $2.50 and when I go to
> check out the order is $12 with shipping.  I'll go to the next one that is
> $6.50 and the total is $9.00.
>

You know there is the feature in the Rock Auto shopping card to choose the
lowest price including shipping (and based on your current order - since
multiple warehouses => huge increase in shipping).  It is a pretty
confusing/badly designed interface, but I got it to work after a few tries.
 http://www.rockauto.com/lang/en/answers.html#alternateparts  - the thing
that got me is you have to select "Minimize cost" then "Alternate" and then
Add Cart to each item that you'd consider.    What was interesting to me
was that often better quality (aka more expensive) parts had less shipping
costs.

Now, if someone has some tales about the minimize cost thing lying, would
love to hear.

Tom