160 ft on air I do a couple of times a year. Not because of costs, but because of not too deep for me to do this 'just' 48.7m on air. If I think it is too deep, I take my ccr and always have a 6/72 diluent ready (poormansmix
), or whatever I have topped up that fits the dive. 160 ft on air on oc is within my holidaylimits.
I have done 200 ft on air also. That is quite deep. But it was a 'trydive' to try what is possible. I layed lines at that depth, did a bottle rotation, all without problems. I have done the same with air diluent (onboard, offboard a trimix if I got narked).
200 ft on air is still normal in a lot of places. Has nothing to do with no money, but with what is teached (cmas allows 200 ft on air for 3* divers) or no helium available.
I agree that 160ft is 'not ideal' maybe. But same with a 30/30 mix on a 30m dive. Or at 31m a 21/35. Helium is rare. Then a nitrox fits better.
But what I said before: discuss it with your team and then decide. Sometimes it has nothing to do with money, but with availability, or with standards of your agency. My choice of helium vs air has to do with responsability. Private vs teaching.
If I have to take a diver on air for the first time to 160ft, then it is not only the air, but maybe a nervous student who never has been soooo deep. Then it is much better to be clear as instructor and have a not narked student who only have to be nervous about his decoschema and not about getting narked or not.