i think dave has a good idea. the way you're doing it now looks like you're end up soft skinning the fingers and the joint would have to be some stretchy material covering the joints. the part that boosts your polycount up a lot would be the spheres, you could easily bring the sphere on the thumb down from 12 subdivisions to 6 or 8 if you're that concerned about the 1000 polys. it's not something that people would notice in game play.

also, if the palm itself isnt going to deform then you could do away with almost all edges running along the z and x plane. you only need the one edge loop that makes it possible for you to make the bottom of the hand. maybe have enough edge loops at the part where the fingers join the hand so that they can sit right there.
Although, i assume the armour piece is part of the palm (if it's not then it should be, it's just hiding faces that will never be seen), that definitely doesn't need all those lines running along it unless you plan on changing it from a square shape.

the fingers don't need to be attached if you're using those cylindrical joints (whether or not it's high or low poly) because you'd end up using a parent constrain on the root of the fingers to the joints rather than soft skinning it.


after saying that i had to be sure that it would actually work...
so in about 20 minutes or so i made this. I'm not sure how the fingers would work in soft skinning but Kurt said that you only need 3 edge loops to make it work...
there are 9 meshes here in total.