I have both 85mm f/1.4 and 17-55 f/2.8.
Both are great lens but they are not exactly the same.
Let me explain.
17-55 f/2.8 is heavy. It is sharp in bright lighting. In low light, the sharpness is still relatively acceptable. I shoot a lot in low light... in this concrete jungle like Singapore, we are not out in the open spaces all the time. So many buildings to create shadows. Indoor the lighting is also not that bright. f/2.8 is good but f/1.4 is even better. 17-55 gives you wide angle and zoom. So it is quite versatile in the sense you can use it to take street, events, scenery, portraits. It is zoom lens so you get the FOV of 24-70 (on DX body or DX mode on a FX body). But it also lack the reach, because not all the times we can go close enough or we want to.
The 85 f/1.4 prime is different. It is very sharp if you know how to handle the lens. It has more depth of field possibilities, the bokeh is another outstanding feature it has. It can't zoom. At a fixed focal length, sometimes either you like it or at times you have might not have the working space to get the shot you want as you might need to stand too far back. It's light. It's good for portraits or street but mostly in a 'controlled' environment. For other areas, some bit of skill is involved to get the most of the lens. It is how well you know your lens, the limits, the performance and how you make the most out of any shots.
So their purposes are very different. Price wise they are comparable. 85mm should be slightly cheaper. The resale value for both lens are great. Usage and how you use the lens is different so get both when the time is right. Or get the 85 first and pray and wait that 17-55 comes out with VR.