With just a little time and a sewing machine, you can hem your own jeans and skip paying someone else to do it.
Do It Yourself Diva's video tutorial above shows a very simple way to hem jeans by folding over the hem and stitching right under the original hem. Perhaps the best part of this is you keep the original hem intact. As such, though, this probably works best for straight leg jeans.
By the way, you can also skip the tailor for hemming dress pants as well -- with or without a sewing machine.