I'm thinking of selling my Alternators as I really don't have the room for all of them. Heck, they've been stored in a box in the attic for a few years now (thankfully the tires haven't cracked and fallen apart), so at this point they're taking up space more than being appreciated. I have mostly the ones that weren't hard to find: Smokescreen, Sideswipe, Hound, Silverstreak, Dead End, Tracks (blister release), Battle Ravage, Windcharger, Shockblast, and Prowl (blister release). Though I haven't committed to selling all of them. I've been checking completed listings on eBay, and it looks like the average price for any of the above is around $15-20 loose. Of course, when I looked a week or so ago, I saw a loose Prowl with only his weapons had sold for $45. It seems like I'm looking at around $15-20 to start out, but how much will packaging affect the price? I kept the boxes intact in the event of storage (lol), so I still have the boxes, inserts, and the two-piece plastic bubbles (Of course, Prowl and Tracks' blisters have been torn off thanks to the collector-unfriendly packaging).
Your prices out of box seem about right, sell them with the box and if they are in good shape you get 20-30+ depending on the figure maybe more. The prices of Alternators have dropped a bit on Ebay, but that could be more the economy. I sold a MISB Swerve last month ( one of the rarest Alts ) for 65$, a couple years ago he was going for over 100$ easy.
last year i picked up smokescreen and sideswipe off ebay for $10. i also got shockblast for $25 and prowl for $35. All loose.
I think alternators Jaguar liscensed car Ravage that transforms into a 4 legged cat. is worth the most on ebay & is in high demand. also the SDCC alternators exclusives are worth a lot on ebay. my favorite is SDCC rodimus. which I own.