Effective August 29, 2021 the U.S. Postal Service increased the price of 1st class mail from .55 cents to .58 cents. You can save .2 cents if you use an electronic postage solution from a vendor such as STAMPS.com.
Certified Return Receipt (CRR) mail, also known as the green card return receipt, to $7.33 (Stamps.com rate) / $7.35 (USPS rate) from the previous $6.96 / $6.98 rate that took effect on . To save $1.20, you can use the Electronic Return Receipt (ERR), which now cost $6.13 / $6.15 total per mail piece.
A nice review of the postal rates that took effect can be found at the USPS website.
Since 2010, there have been six (6) postal increases implemented. A history of the postal increases since 1863 can be found on the following WIKIPEDIA page.