A few things here: 1.) Jeter IP stuff often doesn't pass authentication. Seriously. Same thing with guys like ARod and Pujols. Believe it or not, that's also the case for some of Josh Hamilton's stuff. If you're lucky to get someone like Jeter, ARod, or Pujols to sign for you IP, don't be shocked if it doesn't pass authentication. Does it mean it's not real? No, of course not. It just means that authentication company doesn't want to try and pass it. Not right now, any way, while the player is still hot. Those guys from PSA/DNA and JSA probably don't want that to be known, but that's what happens. I've seen stuff I saw signed by Pujols and Hamilton that was signed right in front of me FAIL authentication from those guys. Now, that brings us to point number 2.) That's also going to mean that stuff signed by those guys is artificially high right now. Think about the market with Mark McGwire about 10 years ago. Big Mac was signing for what, about a grand, back then when he had his one and only private signing in the past decade? Authentication companies were slow to authenticate his sig back then, much like they are today about Jeter, ARod, and Pujols. Today, that's not the case and the price of his memorabilia has gone down.
So, with that being the case, if you trust the source you trust the source. You're throwing money away trying to get it authenticated in my opinion. To me $350 is high. If he could get that money he would have already sold it. I say negotiate. If not, if you're planning on investing $350 I would invest in something like gold...or a vintage autograph.