280k is not a high number for a senior SAP consultant with a big mouth, but 4M indeed is but definitely not impossible or even rare. Anecdotal, but at least I already know 1 person from my own friend group, a friend worked as SAP consultant in utility; he started his own company specializing in SAP for utility but he wrote specific small tools for parts where SAP was(is?) very hard / cumbersome to use or where it has gaps for the particular (big) electricity providers he contracted for. Selling those on the side next to his high contracting fee, he made (makes) millions.

280k is only around $150/hour which isn't unreasonable at all, if anything maybe even a bit low. I know 1099 contractors that bill higher and do less..

Considering he was working in hr, he was probably doing body rental of sap consultant and make the margin on top, if you are good in headhunting is a really scalable business

No, it's really not a high number. It's right on the money for 3 years in-the-trenches experience making the move into consultancy -- around $130-140/hr billable, which is what I was billed out at in the mid 2000s as a .NET consultant.

Pretty sure that he other other employees/consultants under his umbrella. I don't think that anyone bills $4m/yr as a single person (which would equate to around $2000/hr).