Well, for starters, they can't be produced or spawned with CPs. Secondly, you'll be paying one helluva premium. I haven't seen an ARC in ages, but Acclamators go for perverse amounts- 300-400m. Some of the smaller fighters range ,more like 5m and less, but the Hardcell-class Transport has got to be one of the most useful ships out there- and sold for (correct me if I'm wrong) approx. 400m last time one of them changed hands.
The shortest answer about why they're listed is because they still exist in the game, even though they can't be produced. Just as there are rare cars on the road today, the rare ships kind of give an 'authentic' feel to what you'd see on a given day in a given galaxy in SWC.