You are correct, you can buy 10 of these LED's for $2.80 at mouser. However, their cheapest shipping option is $6.95. $6.95 + $2.80= $9.75. Our Price for 10: $6.99 with free shipping.
We just want to make these inexpensive for those who want to make a few of their own Infrared Pens. However, if you wish to purchase more than 10 Infrared LED's then mouser may begin to be a cheaper option depending upon how many you buy.
Please feel free to contact us with any questions you may have.