Consider the example given. On Ymir, valk mants are about 2m in value right now, +9's i guess about 100m.
would you rather
a) use HD for 10% chance for +10, 90% chance to lose ~70m value (+8 is worth about 30m)
or
B ) spend the extra 2m to effectively double your chances to 20% to reach +10.
It's opportunity cost, there is a certain threshold at which it would be much more economically viable to sacrifice gears for improved odds rather than having a gear degrade at a higher rate. Its the same reason its still worth using enriched ores for lower end gears (less than 10m base value normally) in a lot of situations.
Eventually when you reach a high enough upgrade, even sacrificing KVM weapons to help prevent degrading is beneficial (probably only the last step from +13 to +14) since some people have 10k+ "useless" kvm badges. Its not for everyone, but really its not meant to be.
Another idea is that sacrificing a gear doesnt improve your odds, but removes the -1 on failure. It would be fine for things like KVM weapons (i WOULD sacrifice a KVM weapon or 5 at +13 to reach +14) but i would be concerned about cheap gears. If it took 10 attempts on average to go each step 10 -> 20 we'd have waaaaaaaaaay too many +20 gears.
*edit*
before someone says nobody would ever sacrfice a KVM weapon, have a talk to those people that have 10k+ "useless" kvm badges from rolling seals or box events in storage (and are stuck with +12/13 weapons). Its not for everyone, but the absolute best gear is not a casually aquired thing.
Edited by Hrothmund, 09 November 2011 - 03:03 AM.