Hi Howard
I have a Tamiya King Tiger I built about ten years ago still working fine, It cost me 520 back then but it was the full option kit, ie sound, gun flash, recoiling barrel etc. and that could be the difference in prices you found, you can buy the kits without the full option package, all the kits come with plastic tracks, you have to buy upgrade metal tracks as I did, IMO Heng Long tanks will never come close to the Tamiya's hence the far cheaper price, I guess you gets what you pay for, I also have the Tamiya Sherman full option, and a Heng Long leopard that I bought cheap and repaired.