They are pretty expensive. I got mine for $80 at Home Depot. I thought this was a reasonable price. The blade was included as well.
Instead of cutting them with a tile saw, you can use a glass scorer. This makes a faint line, it kind of etches the glass a little. Then you apply direct heat, like from a candle, along the line. You do this pretty slowly around the line for a good 5 minutes. Then you immediately submerge the bottle or whatever you scored in cold water. It will break off at the line. It is pretty hard though. I tried this for some of the bottles but it didn't come out to good.