I found CFAI’s recommendation of 250 hours of study per level to be about right for me. If I did an honest accounting, I probably didn’t hit 250 hours at any of the levels; more like 200. But I primarily used third-party study products (SchweserNotes, Quicksheet, MP3 audio, Secret Sauce), which I think really helped focus my efforts on the testable material. I can sort-of understand how people invest 400+ hours though: if you actually tried to read the original texts, your study hours could easily double. Just reading the CFAI volumes would take me more than 250 hours; those things are as long as telephone books and just as boring.
L3 is very much qualitative compared to the previous two levels. Depending how your brain is wired, you may need to spent much more time compared to previous levels or you may need to spent less time. My brain is wired for quantitative. As a result, I have to spent double the amount of time for L3 compared to L2. Also, the AM section of the paper is a different animal altogether. Don’t underestimate it.