salvia almost never produces seeds, and if it does, germination rates are very low, so salvia is propagated only through cuttings.
: Bouncing Bear Botanicals sells salvia cuttings for 35 bucks, and I bought one, and it arrived in good condition and is now thriving. I live in alaska and its really cold, so they put a 48 hour heat pad in the box they shipped it in. That tells me somebody gives a shit, so I recommend them.