I'm one of those collectors who store their figures in Ziploc bags. I sort bagged figures out by movie and store them in plastic containers in my closet.
I've heard over the years the occasional concern that Ziploc bags aren't too safe to store SW figures in. Something about the long-term effects being harmful, but no specifics.
I don't know of a cheaper or easier way of storing figures in a tidy manner. I personally haven't noticed any harmful side effects on the figures in my collection that have been bagged the longest (mostly POTF2, TPM, AOTC, and POTJ-era types).
Anybody have any evidence on this issue one way or another? I am looking towards the future on this, since for me SW collecting is on a downhill slope. I'm beginning to see the light at the end of the tunnel, and am thinking that the next couple of years will see more funds diverted towards my collection's storage, instead of acquisition.