Check eBay?

Hydros are fairly cheap if you get them done someplace other than a
dive shop... Check with your local fire extinguisher service shop...
If the shop takes your tank someplace else, they are likely to be
overpriced... Ask them if they do it themselves or if they ship 'em
off elsewhere...

This guy has his shipping calculator screwed up though...
http://cgi.ebay.com/Steel-72_W0QQitemZ110023634384QQihZ001QQcategoryZ16057QQrdZ1
QQcmdZViewItem

http://cgi.ebay.com/Steel-Scuba-Tank-With-Sherwood-Valve-NR_W0QQitemZ29002105395
1QQihZ019QQcategoryZ16057QQrdZ1QQcmdZViewItem

Shipping a tank across the country only costs around $20 or so via
UPS... If they are charging much more than that, they're adding their
desired profit into the shipping cost...