I make card sets of 12 with envelopes in a paper drawer box (A2 card box tutorial on SCS)
. At the school auction they went for $25 but people were definitely generous on all their bids that evening. I sold 5 sets at our church bazaar for $18 each an they all sold. I organized them by theme (birthday, thank you, holiday, thinking of you/get well/sympathy, and blank) The decorated boxes I think really helped with the presentation of the cards.
As my best friend says, "Stamping....it's cheaper than therapy" to which I add, "Not by much".
My mom was the proud recipient of my first handmade card. Cost $200.