I bought an induction heater kit from ebay. The total was 36.99$ including worldwide shipping. To my surprise the thing worked pretty well. Without load it oscillates at 100.0kHz with load the frequency dropped to ~92kHz. In this video I am supplying it with 30 Volt from an bench top power supply. The current draw was at about 18 Ampere at most.
The coil comes compressed and you need to space the windings apart. And pay attention to space all windings otherwise you end up wit one very hot turn und burn your fingers. you can see the discoloration at the second winding from the bottom,