Well, honestly, I have spent a LOT of money on drugs. When I would buy them, ecstacy went for $20 a pill, LSD papers were $5 a tab, $10 a gel tab, and I've only done liquid acid twice, both free. Of course weed is expensive, mushrooms were $25 an 1/8 an ounce, mesculine, unfortunately was always free, from my oldest brother, pills of all the sorts were free from my friends that would steal it from either themselves or family members, and speed was cheap, only $10 for 3 pills.
So yeah, I guess you could say it gets expensive, and I've defintely spend my fair share of coniving and mass money on getting them.
Hopefully your woman won't have the same epipheny as me, since mine was legally enforced on me, and didn't stick until the third conviction... I've only failed 1 court summoned drug test, but the worst was failing my pop's tests... Wow, that was some brutal shit, but it got the point across, eventually.
It really wasn't hard for me to stop using them, other than marijuana, since I never really became dependent on any of them. LSD and shrooms are not really addictive, but more of a mind fuck...
I don't know what DXM is, sorry, I've been out of the drug loop for quite some time now, but even LSD paper strength varies everytime. 1 paper could get you insane, or it could take up to 6. Like all drugs though, tolerance can play a big factor on the dosage needed.