And by "expensive", you're looking at north of $3000 per ticket.

Air France and Alitalia are having a "sale" on their premium economy seats (true premium econ, not just the extra legroom and extra glass of booze that Delta's Econ Comfort product is). I don't know what the last day to purchase is, but the last day to fly on the sale fares is May 16th. These tickets would be in the neighborhood of $1600, plus or minus. From the descriptions, PE is similar to domestic F in terms of seat size, pitch, and amenities. (And if it's important to you, you'd get 1.5 miles for every actual flown mile.).

Once you factor in the airfare FLL-XXX-VCE and probably $200 or more in upcharges for Econ Comfort, the differential to fly AF/AZ PE is only about $300 (~$1300 vs. ~$1600). AF and AZ are both part of Skyteam so you'd receive Delta miles for it.