My FH designed ours and used Vistaprint. He just put the design on a postcard instead of a traditional Save the Date format. We were able to get 50 of them for $18 and we used a coupon code for $5 off so $13 total with envelopes.
One of my friends took a nice picture she had of her and her FH together, typed "Save the Date - MM/DD/YYYY" on it using a photo editing software, and printed 4×6's off at Walmart. They looked great, and for less than 50 cents each!
I would go with vistaprint if you want to go have variety and add lines onto your invites. If chosen to continue with the wedding invites, it can be the same or towards another colour towards the theme or décor.
The savings is true based on emails they send you to keep the cost lower
You can get free save the dates from www.weddingchicks.com & print them out at a local print center such as kinos, staples or office depot. Zazzle, shutterfly & vistaprint are also affordable options & often have sales.
I did mine on Vistaprint, about $20 for 30. I did the postcard version and also saved on postage. I got all my stuff when they had a 50 or 60% off sale. They usually have a good Black Friday sale.