If you go the spray can route I would say $10 for Primer, $25-50 for the Base Coat paint, $30 for the Clear Coat and then $50-$75 for decals and you need to factor in masking tape, tack rags, sand paper as well so add another $25 for that. It could cost up to $200. You could go cheaper and use the paint from your local big box store at about $5 per can but I've had some awful results with Valspar, Duplicolor, Krylon and Rustoleum.

On a couple of my bikes I've decided they earned their paint chips so I should just preserve what I have. In those cases I've just lightly wet sanded the frame with super fine sand paper and soapy water and then used Eastwood's Patina Protector to coat it. One can of Patina Protector lasts a long time. I've used it on the bumpers for my Bug and on 2 bikes and still have some left in the can.