My Sykes-Picvant (however u spell it!) set cost over £200 over 10 years ago - as sharp now as they were then, after cutting and earning money on countless heads - also cut accurately around a precision mandrel.
If you want something cheap - car-boot or autojunkle, it'll be Chinese manufacture instead of Indian .....
If its for the odd head - then pay someone to do it properly, also get the valve re-faced while you are at it (even new valves ... there's a reason that NOS was never fitted!).
You should not have to lap the valve in afterwards then.
Related point - SV cylinders distort so much, whenever I've re-cut the valve seat, I've been amazed how out of true they are!
God knows what shape they assume when the are running ?
