I just talked to a very nice UA agent about this.

My original fare was $712. On UA's website it now prices at $527. I called UA and was quoted a price of $608 and offered a credit of $104. When I told her the web quoted a fare of $527, she asked if I had originally booked it on the web. I said yes, and she issued me a credit voucher of $185. Now sitting in coach will be even more bearable.

[By the way... I had this same problem several weeks ago at DL and they said "No way" on the lower web fare. The folks on the DL board thought I was being unreasonable. But, this is just another reason why I left DL for UA.]

I tried to negotiate with the agent and told her they could keep the $185 if they would let me upgrade with miles. No dice.... pushing my luck. Never hurts to ask. She suggested I ask about an operational upgrade at check-in. She thought the chances were slim going to EZE but there was a good possibility on the way home.