That is a huge difference. 400ug is a big dose and 50ug barely noticable.
Anyone reading this without experience going for 400 is going to get knocked for six
Some research suggests a “30-40 microgram trip first, then a 60-80 microgram before anything larger, then a 120-140 microgram before anything larger, then either stopping there (this was the dosage that resulted in the highest increase in well-being) or doing a 170-240 microgram trip.” — https://tripsafe.org/how-to-take-lsd/#start-small
I'm just arguing that it would make more sense to start at 80-110-140-170 etc because below that is placebo.
Source: have worked directly with LSD crystal in the past. (Unfortunately anecdotes are king when it comes to illicit drugs otherwise I’d be able to cite an actual external source)
This is probably the best way to describe the therapeutic value in this situation. Hallucinogens (not just LSD), give you some distance from your headspace. It's not to the degree you feel depersonalized or have an out of body experience, but it allows you to examine your own thoughts without all those underlying assumptions that you hold yourself to subconsciously, every day.
As far as I can tell, from my own experience, lsd kind of make you see your own actions/thoughts as an observer[0], it's a very useful tool if you're into introspection. If you're not used to introspection it can be quite unsettling though.
[0] >50ug <400ug, after that you just look a the ceiling and enjoy the lights