Emails cost nothing to send, mail costs next to nothing. If a college spends a maximum of $5 enticing you to apply, saying you are a promising candidate, filling your head with dreams of stepping onto campus, and you apply, you have put $70 into the college’s pocket. And imagine if you attend! The college just made $250,000 off of a $5 investment in you.
No, the letters don’t mean anything. Colleges want to generate money from application fees.