Most people don’t realize that the price list from the United States Postal Service is over 70 pages! There are countless categories and of mail and within each, size, weight and destination affects the price.
I generally tell people, the postage cost increases if your mail has to travel further distances.
Just take a look at page 16 for First Class Letters and Cards–aside from the weight, there are costs if Automation mail, Machinable vs Nonmachinable. Under Automation the 5-digit, AADC and Mixed AADC refers to the concentration of mail going to the same area.
So postage for a 1 ounce letter mailing can cost anywhere from 38.3 to 42.8 cents each, depending on where the mail is dropped and where it’s final destination is, among other things .
Notice 123 • Effective June 23, 2019
For this reason, it is helpful to see how and where a postage increase will affect specific categories of the mail.
Thankfully a recent article in the most recent Mailing and Systems Technology magazine offers a visual analysis, How will the January 26 increase affect your budget.
Thanks to Adam Lewenberg’s analysis, we can see the specifics of the Jan 26, 2020 postage increase. Large envelopes weighing more than 2 ounces will be most affected with price increase of 4.3 – 21.4%. 
In fact, larger sized envelopes will see an increase across the board, especially nonprofit flat sized mail seeing as much as 14% increase.
Please feel free to contact me if you have a quick question about pricing, darci@dirmailserv.com.