Can the IRS Save on Postage?

We recently received three envelopes from the IRS that measured 10 inches by 15 inches. Each envelope contained a one page letter. The postage on the envelopes was $00.88, $1.05, and $2.41. Is it really necessary to place a one page letter in such a large envelope and expend more than $00.44 for the postage?  Regular postage would have saved $3.02.