Hey, Cindy!  This is a tough issue...if you do this as a career or even a second income, try reminding them that you rely on this income to pay bills.  I offer my friends & family a discount so they feel "special" but still have to pay for the cake and the time I put into it. :)  And if that doesn't work...maybe you should be "unavailable" on the dates for which they request cakes.