Our vet advised chipping over tattooing because he said he's seen many dogs whose ears had been clipped off by thieves to remove the tattoo.
Microchips were just being introduced into our area 8 years ago and our vet only charged us $5! What a nice guy! Sherman was already chipped, so I don't know his $$.
Definitly check out your humane society for a chipping clinic - I think it's round $15.00 here during a clinic.