What does it actually cost me, the seller, to sell?

Main seller costs: agent commission around 2% + 5% VAT, the developer NOC fee (~AED 500-5,000), and, if mortgaged, an early-settlement fee capped at 1% or AED 10,000. The 4% DLD transfer fee is customarily the buyer's, though the MOU can split it. Also budget a few thousand dirhams for trustee/admin and clearing any service-charge arrears before the NOC.