This is a bit of an odd request. Usually riders who slam their seats all the way down are doing so for trials, dirt jumps, urban, etc... not the same crew who usually worries about the grams. But getting a cheap seatpost and hacking off everything but a few inches at the top is a cheap option.

If you do like to put the seat all the way up occasionally (for the ride home from the trails, etc) you can go with a cheaper road post... but then if you ever hit anything with the post up, trouble.