I've been looking for a long term solution to keeping a price tag on carvings sitting in my display area. Rain isn't a problem for me but intense sun and wind are. Paper tags are quickly blown away, or to pieces, so I decided to try plastic tags.
The most durable plastic "price tag" I found was in the garden shop at hardware stores. Those plastic stakes with a square area on top for writing about your plant species... Those held up well when stapled to a carving BUT apparently PERMANENT MARKER doesn't mean what I thought it did

I am amazed at how quickly Sharpie ink faded to nothingness.
"Paper or plastic?" How about neither?
Aluminum appears to be my best bet yet!
Permatags are an aluminum tag used for marking trees, mining claims, soil/rock sample locations, etc. You write on them with a ball point pen to emboss your price into the tag, staple it to the carving and you're covered for a very long time.
I've used permatags for claim staking throughout Nevada, Arizona and Idaho. The only time I know of them "failing" is when the ravens pull them off a claim stake. As a price tag, the shiney tags attract the eye of would be buyers

Permatag can be purchased from geology or agricultural supply stores and online for about $20 per 500 pcs. I prefer the tac-on rather than the tie-on.
http://www.lmine.com/mm5/merchant.mvc?Screen=PROD&Store_Code=LMS&Product_Code=13310&Category_Code=al-tags
Butch Elrod - WoodHacker.com
World Map of Chainsaw Carving Artists