We made some signs for our course and it wasn't too bad in cost.
We developed designs in Word, printed out on Photo Paper, then laminated them. When cutting the laminating sheet ($15 for 50), leave enough space so the seal around the paper isn't compromised. Basically, leave about 1/2 inch around the edge. If you trim the laminate all the way up to the photo paper, water will definitely get in and make the ink run.
I got a small piece of birch plywood ($15) cut into as many 8 x 10 pieces as possible, about 25. This matched the size of the pre-cut acrylic sheets ($2)Lowe's had. Then prime and seal the wood with Kilz exterior ($15). I used some small nut, washer, and bolts to attach the acrylic sheets to the wood.
In total about $100 bucks, that's not too bad and they're holding up nicely!!