I've seen two or three other threads on other forums that have around $1700 total for the whole coupe. $500/side seems to match the figure for the doors; so your $1800 for parts seems in the ballpark. Distinction between OEM and aftermarket buyers was listed as the "velveteen" surface on parts from the dealer vs a smooth rubber from the aftermarket, but you pay for that difference.

I have to assume the sedan parts are simply much more available and cheaper.

Since San Antonio is in the midst of a historic drought, and the coupe is currently my project car, I've got time to shop around.