Depends on what you want to use it for. I received a small light pad for Christmas last year, about 10x12" and less than 1/2" thick, and it's great for small to medium appliqué tracing. It has a USB plug in and I had to use one of the transformers from my phones for it; it didn't come with one. But I'm quite pleased--it helped me finally finish my "18 years of Christmas" quilt.
I'm pretty sure it was bought on Amazon for less than $20.