it does save you 30 copper per use.. but you also lose 5% chance of getting upgrade.
lets use Glob of Ectoplasm as an example. theoretically if you will only ever get one Glob of Ectoplasm each time, you will get...
Rune- cost 30 copper x 100 use = 3000 copper = 30 silver 20% upgrade meaning 20 Glob of Ectoplasm
Silver- cost 60 copper x 100 use = 6000 copper = 60 silver 25% upgrade meaning 25 Glob of Ectoplasm
Glob of Ectoplasm atm worth about 21 silver each, Five extra Glob of Ectoplasm will earn you 21x5=105 silver. menus the cost different 105-(60-30)=105-30=75 silver
75 silver= 7500 copper
7500 copper / 100 use = 75 copper
If you use Rune on rare,exotic you will lose 75 copper on each break down.
p.s. if you don't care about the upgrade, you could always sale them for more gold... just saying.. or you can sale the equip directly......