Buying lead weight.
If you are taking about the dive industry now. no ones buy lead weight anymore because most resort would provide. but in the good old days when i first started diving in the early 90's.
If you want to learn diving, you have to buy your own basic gear (mask, snokle, fins, weight belt and weight) because no rental is available. i still have my own private lead weight at home :) have converted them into paper weight
you can't say an instructor is from hell just because he ask you to buy lead weight, anyway if you have your own next time you go dive can ask the operator to charge you cheaper as you don't even need to use their weight. FYI the weights you used during dive trip is not free, operator factor the rental into the package. And in some places of the world no weight is provided. "BRING YOUR OWN"
'bring your own weight " not a very clever dive shop advertising isnt it ? unless it is a expedition to Skull Island or something.
Hard to belive !