I'm betting that what really happened goes something like this: a body shop took a smashed up or used up V6 that was purchased on the cheap, gave it a hood and paint, stuffed a 289 they had laying around into the engine bay and, i'm willing to bet, attached it to the V6 tranny/rearend.
then said man/child/fool who knows little/nothing about cars, let alone mustangs (we'll call him the 'chump') purchases a "fast" car at the recommendation of shop staff while bringing his car in for repairs, and they laugh all the way to the bank because i'm sure they charged him somewhere near that reserve price. OWNED!
forgot to add that the price is likely reflective of its quarter mile time. 1000+ dollars for each second you cruise down the track seems reasonable...go cobra go
also worth mentioning that a brand new V6/5 speed started at 13/14k in 1994. makes that buy it now price of 17000 even scarier.