There's no cost associated with "training" because there is none to be done. Handling is not recommended because it can be entirely too stressful for chams. And it's not like mammals where they just get used to it over time. Reptiles don't work quite the same and it just continues to be stressful until they can't take it any more. Sometimes it causes them to be ill and stop eating. Different chams have different personalities - some hate the world and cannot be handled and some seem to enjoy the interaction. I have a veiled that fits the former and a panther that fits the latter. And I have a jacksons that falls in the middle. But I know lots of people who have veiled who are very friendly and panthers that aren't. It just depends on the individual cham and you can't do much about it. If you're looking for a pet that can be handled frequently you'd be much better off with a gecko or bearded dragon. Chams just aren't cuddly creatures!
I personally Haven't seen many cuddly geckos or dragons either though, so I don't see why people would recommend them when some one asks about taming chameleons. You don't tame wild animals but you make them more tolerable to you and their surroundings. As an owner of reptiles , Not being a threat is probably your biggest key into gaining the trust of your animal. Routinely cleaning feeding and other non handling activities should be enough over time to let your chameleon know your not a threat. Having them young with proper care they should tolerate you but as any species some are just pricks and dont like people or other things and will show you. Like cameras, vaccums ,showers ect. You will get to know your chameleon and you should know what it likes or dont like over time.
There is plenty of cost for good training. It's expensive too.. Im talking food and proper setup... not on practicing to jump through hoops : )