everyone with natural selection 2 pre order got free copy of NS2 so is worth now something like 10$ even less
Yes, it's more than enough for CS:GO. I've seen an offer of CS:GO+2 Borderlands 1 GOTY for it, so don't go for less than that.
No, not everyone. Only those who preordered it before it came to steam got a free copy, which was only about 40k people. It was also $35 back then; so it's worth AT THE VERY LEAST $17.50.
No, it doesn't. But the digital deluxe edition is $40, so I don't see how that comment is relevant.
(I realize that preorders upgraded to digital deluxe as well, but those cost $25 to the buyer and cost more now on steamtrades, so it's still not a relevant comment)
Swedish pack (row gift 10 games) or Bitcomposer pack (row gift 5 games) for NS2
Clear Trade.
Title says it all.