Amazon prices - list price versus our price

I’m getting the XML from Amazon through their associates program.

For any one random item, the msrp price is $219.99. Then the list price from Amazon is $89.99. But “our price” on Amazon’s site fluctuates (it has changed three times today). I’d like to list the “our price” on our site, so that our prices would follow their fluctuations, but I can’t find the right variable in any of their response groups.

Any ideas?