Reddit user Pengastorto posted this very helpful guide to just how useful Baron Buff is.
"So we all know that baron is one of the most important aspects of this game. But do you know exactly how much it is worth?
Here is what everyone single person on your team gets from the buff:
40 ability power 40 attack damage 3% of your maximum health in health regeneration per 5 sec. 1% of your maximum mana in mana regeneration per 5 sec. 300 gold and 900 experience points
If you turn those stats into gold, you'll find that:
40 ap = blasting wand = 860
40 ad ~ Bestfriend sword = 1650
3% of health as regen/5 with 2000 health ~ 60/5 = 4 regrowth pendants = 1740
1% of mana as manaregen/5 with 1000 mana ~ 10/5 = a meki pendant + a faerie charm = 570
and lastly the 300 gold.
(*note that an average champion would have around 2000 health and 1000 mana.)
If you add that all up, the baron buff gives at least 5120 stats worth of gold, TO EACH PLAYER! In total, baron grants your team a possible 25600 gold lead!"
This is pretty great, I absolutely had no idea that the gold value of this buff was so high! Thanks Pengastorto!