With a certain amount of schedule flexibility, you can get FC fares for under $700 roundtrip. Even if you can't travel midweek, it's not that hard to find FC fares in $800 range. Although $700 Main fares are going to be pretty high up the fare class hierarchy and would expect a Plat has decent comp upgrade chances on those (Plat AMEX card doesn't help, only DL Amex Reserve is a factor and only after fare class).