Looks like a common typo, but chances are slim someone
would type in the .net, more likely they would type in the
.com. The best thing for you would be if supplement.net
got developped into a high traffic vitamin site, then you'd
get some quality typo traffic. Or, develop your site a bit and
try to get good ranking for 'suppliment', and get some search
engine traffic for that term. Right now would be hard to get
more than xx for it. good luck