Honestly I'd just drop fortune entirely, or the tool entirely for that matter. While it does make a minor change to it's usefulness in regards to farming, there are plenty of work-arounds for that. The main application I can see for this particular tool would be the endless mob-killing it could bring in, as the other enchants are already available or have a way to make it around anyways without the need of an expensive star tool. However with endless mob-killing brings it's own issue, that being it simply screams automated. So while it has potential to be handy, pretty much every application of it has a applicable work-around already in effect. Even the mob-killing in fact, although it does require ExtCommands++, which is assumable only a few hundred thousand ECD more than a 1500 NStar Star Hoe with considerably more applications.
Who said the Star Hoe would be 1500 nstars, again? I dunno, put it at around 1/3 the price because of it's usefulness. But, @rax_tue, your mention of the star tool brings up a good point, but here's the thing. 2200 nstars for an OP sword, or 500-1000 nstars for something that'll cook any meat for you, and give you more drops from both mobs AND crops, and won't take damage from either of those two things, so you won't ever really need to repair it. What's the server price and fortune 3 drop rate for nwarts, just curios. Nice trivia, too!