Hemming with the original hem means just that...keeping the original hem on the jeans. The excess can be cut (see Nola's guide
here), or it can be folded up inside the jeans (
this method). They are both referred to as hemming with originals. Hemming without the original hem means cutting the jeans to the desired length, and doing a plain hem. The cost really depends where you live. For original hem, it can run anywhere from around $9 to $30. I usually wash and dry before hemming to avoid any possible shrinkage issues.