This is just my personal opinion. If people respect you, they will send you QSL cards with good design and quality. Then, if you return the card, even if it's not perfect, it at least shows some consideration. My own printed QSL cards cost 4.5 yuan each, plus postage of 6 yuan, and a few dollars for an envelope; 100 cards would be negligible in cost. The cost to send one QSL card is only around 1.5 yuan, which is very affordable.