Cost and cell count used to be a factor for me too, but here's one way to get past it.
Buy a new pack of of liquid yeast and pitch it into a low gravity beer, like Centennial Blonde or an English Bitter (assuming you are using 1056/001 or 1968/002). When you rack your beer off the yeast cake, fill up a 1 pint mason jar with the slurry and throw this into the refrigerator until you're ready to pitch it into your next higher strength beer (I try to repitch within 2 weeks, but research detailed in one of the threads below suggests you could go out much longer than this.) And don't bother washing/rinsing it, it's not necessary and may do more harm than good. With this process, you don't need to ever build a starter and you can reuse your yeast over and over if your sanitation kung fu is sound.
Here are a couple good reads if you're interested in the process:
https://www.homebrewtalk.com/showthread.php?t=519995
https://www.homebrewtalk.com/showthread.php?t=166221