Since you reg'd it today, a good rule of thumb is that it's worth about the same as you paid a few hours ago... That is if you can find someone willing to buy it from you, rather than just reg a similar name themselves at their registrar of choice.
Some niches in 7N have sold out and those are worth a bit more.
Longer term, I'm a holder of many palindrome and 888 havin' 7N ... So I do have decent hopes for the category as a whole.