Yes, dollar store 2/$1, head there a few times a year and stock up. Except boxed Christmas cards I get at Hallmark or Costco 50% off after the holiday for the next year.
Send birthday and Christmas cards to all family members, most major holiday cards to my kids with $, easy way to give them a little something through out the year.
I also send cards to friends and family for other life events.
I have two long time friends that I exchange cards with letters in them a few times a year. Fun way to stay in touch along with email.
I enjoy receiving cards, too. DH and I keep received cards up for about a month. we like to see them, especially the hand made ones from the grandkids

My Mom showed me how to make little boxes out of cards, so sometimes those are fun to make with old cards and use for small gifts (jewelry, folded $bills, etc)
Maybe it's an age thing? Younger folks don't seem to send cards. Neither of our kids send Christmas cards, nor do our nieces/nephews.