There are plenty of answers already, so there will naturally be some overlap between mine and what's already said, but I hope to be able to give some food for thought anyways.
First of all, judging by the way you express yourself, both on the OP and the comments, you seem to be quite agitated by the situation. Before you do anything, you need to find a way to calm down and try to think straight. Don't take any rash decisions, in the heat of the moment. As others have also eluded to, it might have detrimental and unexpected effects down the road. That's step 1.
Then let's unpack the situation, you are in a lab where there is some research is carried out. On this one project you feel you have more hands on experience on a field/method than the PI. The fact that your PI trusts your knowledge and brings you in is a very positive sign. Second positive sign, I believe, that you are in a lab where expertise is shared and people contribute to each other's projects. I have worked in intellectual isolation long enough to appreciate how valuable that is. Try to reflect on that a bit, that's step 2.
I think your frustration is justified. However, it is not uncommon that situations like these happen. What counts as authorship varies ALOT between labs, and even among the research groups at the same place. That is just a fact. It's a bit of the culture that the PI fosters (or allows) within the group. Also, don't even question on why the PI is on the paper, that jsut is the case, s/he pays for all of you, and has likely contributed to writing the paper. You might disagree with it, but it simply is the case. I think it would be fair to say many users here at AC.SE have experienced one or more cases like this.
Once you have calmed down, what can you do? The way I see it, you have two options:
Accept the situation and commit to the existing culture. Again, you don't need to agree with it, you just need to get through. Play the game with the rules others are playing, if you want to keep playing. Next time you get called in for your expertise, establish the mode of collaboration as the first thing, before you commit. Otherwise, learn as much as you can, get your projects done and move on. Next place you go to, you can (and likely will) pay more attention to these kind of things.
If the situation really doesn't sit well with you and you don't think you can work effectively in that place anymore (in other words if the bridges are burned from your end) then you can certainly complain and "fight". I think you can make a case, but my guess is that nothing will really change with respect to this paper. But you might seriously hurt your position in your group. If being right is the most important thing for you, then surely whatever we/your PI/head of the dept will say won't make it better.
This reminds me about that silly joke, if you are in a fight with your spouse you can be either right or happy, both not both. Choose what matters most for you, and go that way. There will be consequences either way, I feel.