FYI you should be able to send videos via Media Mail which would probably be more like $1.48 in postage instead of $4.14. (Don't forget to add in the cost of envelopes, too.
)
This does take longer than first class mail, so if you specified that you would be shipping them via first class mail then you might not want to use Media Mail.
Check out USPS.com for their rules regarding what qualifies as Media Mail, but I know that books and CDs/DVDs qualify. The only catch is that you have to physically go to the post office and ship them from the counter
in person. (So if you are doing one tape per day, it may be more hassle than it's worth.)