If you look on .io market you can see that only strong single words with substantial meaning to tech industry makes it over x.xxx. So in my opinion 1.000 USD for packers.io seems very good to me. If he buys it with intention to develop anything connected to NFL Packers then have potential TM in mind.
Agree, $1K sounds like a good deal. Especially if this domain has received no other interest. But of cause always try out with a reasonable counter offer