I'm pretty sure the answer is that you don't earn EQD through MCE purchases, but I didn't find anything definitive on FT and the AA site is not 100% clear:
Do checked bag fees, seat purchases, 500-mile upgrades or other products/service fees count toward earning award miles and EQDs?
No, only the base fare paid for your ticket including any carrier-imposed fees will count toward earning award miles and EQDs. Fees for other products or services will not be awarded miles or EQDs, including but not limited to the following: checked baggage fees, Admirals ClubŪ memberships, Wi-Fi passes, in-flight food and beverage purchases, in-flight entertainment, unaccompanied minor fees, pet travel fees, 500-mile upgrades, mileage upgrade cash co-payments, Mileage Multiplier, BuyMiles, GiftMiles, ShareMiles or other mileage purchases, ticket change fees, ticketing fees, same-day confirmed flight change or standby fees and service charges.
https://www.aa.com/i18n/aadvantage-p...jsp#awardmiles
So is purchasing MCE considered "seat purchases" for EQD earning? Or do you earn additional EQD when purchasing MCE?
n.b. the reason I ask is that my step son just booked his last trip for the year and it will put him at about 27,000 EQM and $2980 EQD. He's wondering if buying MCE will push him over $3000 EQD and get Gold.