The recent postage increase is just the first of several expected over the next few years. The USPS is projected to lose of its first-class business to the Internet—which means they will have to raise their prices to replace this lost revenue.
The book (page 138 - Move to the Internet) suggests you cut your mailing in half over the next few years by using the Internet more to market your show. To accomplish this, use a two-pronged strategy:
This year we suggest you budget 5% less postage costs for all your shows. Next year 15% less and so forth until you achieve the 50% reduction.