If you are looking at custom signs, you are paying for the sign and the vinyl graphics that go on it. Vinyl is sold by the square foot and the more writing they can get on it, the cheaper it will be for you.
Ex.- Depending on letter size and font, "No Trespassing" might take up 3ft of vinyl. If vinyl is $9 sqft and the sign itself cost $2, you end up having to pay a lot of money for a little sign. 3x9=18+2= $20, then throw in some labor for them having to apply the graphics and you are at $30 pretty fast. I worked at a sign shop for 8 years and we tried to avoid the little signs because it was labor intensive and cost the customer so much. We sent them to another local company that had more vinyl cutting machines, more employees and bought more of that type of material so they could do it cheaper. We did more large building signs and temporary neighborhood signs.