When I ship my cards 1st-Class air mail bubble mailers from Hawaii to the continental US, it is usually a little over $2 for shipping, with it being around 1.30 for the shipping itself, plus 80 cents for the Delivery Confirmation. However, if you are shipping cont. US to cont. US, I'm sure it'll be cheaper.
As far as what materials you use, it depends on how much you want to spend. The bubble mailers I use, I get from one of my jobs at a discounted rate, so I get them fairly cheap, but they can be anywhere from 50 cents to $1 each, depending if they are bought singly or in bulk of course. I prefer having the card in a sleeve, then top-loader, then wrapped in a half sheet of bubble wrap, taped on all sides, then placed in the bubble mailer.
I know this may seem superfluous to some, but it gives me peace of mind that the card is secure and a lot of my buyers seem to appreciate the effort.
Wall mart has bubble mailers 10 count for $4.44 in my area. Its the best value unless you bulk order them online.
USPS first class should be anywhere for $1.04 up with most my orders being about $2.02 or so due to weight stuff.
I typically add dc to a first class shipped bubble envelope which is slightly less than $3 total usually. The DC is great for protecting yourself from ripspers (if you send second, if you send first it just helps you file mail fraud.)
Right, bubble mailer with DC sent first class (which is usually 4 days max from one side of the country to the other, usually less) is the best way to go about it.
Also, it's easy to reuse bubble mailers. Just cut off one end when you open them and when you send back use some paper and a lot of tape (enough to make sure no water will get in) on the edge you cut. I do this ALL THE TIME and nobody has ever commented on it. Cheap? You betcha. But it works and I feel if done right the cards stay protected.
A bubble mailer's really not necessary for small amounts of cards. Honestly, a toploader isn't even really necessary, although I admit I still use one for expensive cards just for peace of mind.
I sell cards reasonably often through eBay and have yet to get a single complaint about card condition just by sending the cards in regular sleeves. I fold a standard piece of computer paper in thirds to fit in an envelope and tuck the sleeve of cards into the middle of it. Works just fine.
I've never received cards damaged in a standard envelope either.
If you're sending too many cards to fit comfortably in a standard white envelope, that's a different story.
it depends on how many i'm sending. If it's just a few then i'll put them in those hard plastic sleeves, tap em bck to back and wrap 2 pieces of computer paper around the cards, and ship in a standard envelope. If it's a good deal of cards then i'll put them in a ziploc baggie and wrap the extra baggie around the cards and tape it down, then bubble mailer it.