From the announcement:
USPS is going to be increasing their rates at the end of the month, so we're going to have to increase our Flat Rate shipping price and our Free Shipping amount. Starting June 1st we will have a flat rate of $10, and Free Shipping at $150+.
In the meantime take advantage of the current lower rates and enjoy a 10% off coupon starting today and lasting until May 16th! Use the code 'MAY2015' when checking out.