Right, the extension plays a large roll, but it will give you an idea. If the .net sells for $50k, then the .com is worth more thn $50k. If the .net sells for $200, well then the .com is worth under $5k. Im not saying they are worth the same, but I am saying it will directly correlate.
Well, premiumhost.net sold for just over $300. (http://www.sedo.com/auction/auction_history.php?language=e&auction_id=2251&tracked=&partnerid=14460) Based on that, I would put the value of premiumhost.com at low/mid $XXXX (roughly $3000).
premiumhost.net had potential to be sodl for a lot more then $310, if it was brokered instead of auctioned it could have gone for $1,000 or even higher. It should have been marketed to the audience on webhostingtalk.com. As for the .com, the bad choice fo venue for the .net will nto necesarrily hurt potential of the .com if sold correctly. Find a good broker and have him market it, don't settle for teh easy way out by putting it up for auction.
All domains have the potential to be sold for more, but whether they do or not depends on the buyer. A domain only worth what someone is willing tot pay.