Tartan, like pretty much everything in life, you have to "do the math" to figure out if it's worth having the fabric shipped across the border. We charge $12.50 per envelope - and the envelope holds 8 yards of fabric. Then Canada Post charges the $5 cross-border administrative fee when they deliver the package, which brings the cost of that envelope to $17.50. They also charge HST/PST/GST on the value of the contents, but you'd be paying that tax even if you were buying the fabric locally.
Anyway... dividing the $17.50 by the the 8 yards of fabric, that works out to $2.19 per yard. If you add that to the price per yard of the fabric, then compare it to what you would be paying locally, you will have your answer as to whether it's worth it to order online.
I think the key is to fill up that envelope. Not all US shops will fill it to the max, but we do, and it works. :-)
I understand that some branches of the US Post Office have given shippers a lot of grief about the "fat envelopes", but we don't have any problem getting our envelopes shipped. :thumbup: