I only weigh any of my snakes if it's needed to calculate a dose of medication, which happily that hasn't been for "ages"!
EL-Ziggy, I'm with you- I don't understand the routine snake-weight obsession either. I don't weigh their food either. Shocking, I know....
But with feeders, I know from experience what size prey to feed- many of our readers do not, so that's probably the best way they can know for sure.