I am trying to amend my tax return as I accidentally filed and didn't realize I still had a form I hadn't received yet. That for is a 1099-MISC - I MUST upgrade??

Yes. In order to file the 1099 it would require you to upgrade to file the amended return. Also just a side note you must send your amended return in by mail.

So I have to pay $89.99 to file one form? That is ridiculous, I just paid $39.99 to file my taxes. Can I use another tax outfit to do my amend?

Yes you can choose to file the amend elsewhere if that is what you want. At a minimum you would need the Deluxe version, which is $59.99 to file the federal return.