Normally a SkyClub pass will cost you $50. Now if you have the Delta Platinum card it is just $25 for a one time use. Or, if you have the Delta AMEX Reserve card you can get in free but are technically not a member.
If you plan to fly a bunch for 30 days you can get a 30 day membership pass. It will run you $90. But for now you can use code FB30D to get 20% off and spend just $72! HERE is the link to get the deal.
Also as a funny side point, I often get e-Mails and comments when I slip and call the Sky Clubs by the old name Crown Rooms, but look at what the Delta.com URL is for signing up for Sky Club membership! 😉