The new retail rate for parcels will be $3.50 (up from $3.00), and it covers up to 4 ounces

The retail rate is what you pay if you go to the window or use your own stamps. If you use a commercial service like Ebay, PayPal, or Stamps.com, you pay a discounted commercial rate. That rate will be rising from $2.61 to $2.66. It may be time to consider that option.