Hi,
If 30 Amps is enough, let me recommend Allegro's ACS712, which goes for about 2 EUR/pcs at 100+ quantities. I have used it in a couple of projects and it really is a good performer for the price, which is less than the price of similar ready-to-use current tranformers that I have found. Also it is more compact and easy to assembe as a SMD soic8 package.
With hall effect sensor you must remember that all magnetic fields interfere with the measurement. Don't put any other high current traces or wires near the sensor, and if you want the best possible performance, you may need to filter out the effect of earth's magnetic athmosphere.
-Samppa