After going up this past January, the cost of mailing a letter or a postcard in the U.S. is going to cost a little more this weekend. The cost of a first class stamp is going up by three cents, from 55 cents to 58 cents. The price change officially happens Sunday. “I don’t know why,” Lamesa Postmaster Richard Hinkle said about the increase. “They don’t give us an explanation. It’s a yearly increase, I guess.” The price increase only impacts first class mailed letters, postcards and mailing services. It does not affect first class package service or priority mail, according to the ...