I think editing a 50MP image falls under "people who need the utmost from a Mac". 
I'm not saying that an iMac can replace a Mac Pro; I'm just saying that the user base of the Mac Pro has gotten smaller over the past few years as consumer level computers have gotten more powerful. Even a consumer level computer may suit the OP's needs.
I'm not saying that an iMac can replace a Mac Pro; I'm just saying that the user base of the Mac Pro has gotten smaller over the past few years as consumer level computers have gotten more powerful. Even a consumer level computer may suit the OP's needs.