I bet if you look at your past, favorite pics you will find very few shot under 50mm. If you are looking at this from a business investment point of view, that is your only starting point.
The canon 85 1.8 is an incredible value. It is easily my most used lens. I just evaluated the new sigma 50 and 35. If I were a hobbiest, the 35 would be my choice, but as someone trying to make a living, it has to be the 50.
Since picking up the tokina, I don't use the 24-105 under 35mm. 24-105 is a good kick around lens, but it has kind of lost its polish so to speak. I only use it at run and gun events now. I have no experience with the 28-135 but would probably suggest keeping it, and planning to phase it out over time.
Again, look at your most often used focal length and go from there.