"So, the stats show that Low passage (as written) wouldn't exist as anything but a rare situation where someone is escaping great danger due to the high death toll."
Not even that reason because Fast Drug is, in all ways, better.
I just looked over many of the CT books and found no mention of combat drugs unless there in an unrelated section. As a matter of fact, They talk about causing damage, effect of damage and.. nothing about healing damage. Even the medical skill entry has no game mechanic. No mention of drugs in general let alone Fast drug.
However, MegaTraveller has extensive drug lists. Fast drugs is there and it's feature are thus:
Your functions are slowed, but not suspended, at a rate of 60 to 1. You still must consume food and breath. In this state, you are "extremely vulnerable", in other words, you are useless for 60 days. It also says upon ingestion and effective immediately the dose lasts sixty days.
Now there's an explanation for Fast drugs and why it's not really a substitute for a low berth even at 1/5 the price. You still take up normal space and still need life support, you need constant attention and your wounds and illnesses aren't any better off. It's a 'cheap' way to save some life support but overall not much. This explains why merchants, naval organizations and pirates prefer low berth.