If you bought some other product (eg. computer) and it went on sale the next day, would you expect to be refunded the difference? I think VX have been very generous. BTW - I've noticed sometimes it is more expensive to book an Air Canada fare on a weekend. Virgin Blue in Australia is well know for it's "Happy Hour" fares (well at least it used to be).

If you really feel you deserve a 'refund', you can try upgrading to an F fare (no change fee). Then downgrade to the cheaper Y fare and you should get a credit for the difference. The problem is that the money will be tied up as a credit and there is absolutely no guarantee it will work. In theory it should work, but I've never tried it.