Ok, 4 bottles of chemicals for $60, lasted over 10 years so far. At present I'm at $6 per year and only about 3/4 of the way through... At that rate it will end up costing me about $4.00 per year. Much cheaper in the long run to use chemicals...
Don't have kids and I obviously know what I'm doing as my fish don't die either.
As previously stated, if you know what you're doing chemicals are safe...
It's like anything, if you don't know what you're doing, best not do it - common sense really.