"Target rate" means nothing I've found. Broker could be keeping 50% of that load or as little as 10%. You never know. I've found what works best for me is #1 never haul anything you think is cheap. #2 if the rate is too good to be true, it prob is and comes with a ton of headaches. #3 know your true cost per mile to operate. #4 see what that lane averages and personally I never go much below that.
#3 is the biggest imo. If you take a load you're happy with the profit you make on that lane that's really all that matters in the end.