The email is legit.
The sale price is not shown on the page where you buy the tokens, but you will get the extra data a few days after the purchase, when you purchase the tokens within the sale period. For more info, see this thread.
If the DSS number you have posted is your HN account number, please edit it out of the post; you don't want this number posted for everyone to see. If the reps on the site need your info they will ask you to send it to them privately.
We received an email for Data Token Madness - You can buy 4 - 8 - 15 - 35 GB Tokens at reduced rate. The note looks official but I'm starting to wonder if it is junk mail. I cannot get the special price by going my ordinary way through the HughesNet App. I have bought some at the old price because we are desperate and have also sent the email to Hughesnet that says they will answer in 24 hours (did this twice). Have had no response. Thanks for any input. Karen