the first ones all right , the other 2 are rather sucky.. i wouldnt register the last 2 if they were available..
Domains are like real estate they are worth exactly what the purchasee is willing to pay
With that being said platinum18.com is worth holding on to at the very least .. I wouldnt sell it for anything less than 1k, it doesnt cost you anything to keep so start the bid at 1k , and if nobody buys it only costs you $7 to renew