Once you have your card designed at 6×7.5 and saved as a high quality jpeg, you can upload it to Costco for printing (see this post for card ideas). My understanding is that you can order these and have them delivered via mail if you aren’t a member at Costco.
I know it can be tricky to figure out how to do it, so I thought I would post a little tutorial:
You will need to set up or log into your account in the photo area. Then go to 6×7.5 Greet Cards:
Click on the more tab and then select the Custom Template:
Here’s where you upload your card. If you designed it 7.5×6 instead of 6×7.5 then you might need to rotate it after dropping it on the canvas:
Once you’re happy with it, click continue. Click through the rest of the screens making sure you double check settings and your photo. Then just add to your cart selecting how many you want. You have to order a minimum of 50 cards for $14.99 including envelopes, then you can order quantities of 25 after that.