When to use the 40% gem quality to GCP recipe?

Hi

I'm wondering what people think is the 'cutoff' point for when to stop using the 'total 40% gem quality to GCP' vendor recipe.

For those not knowing the vendor recipe, if you vendor skill gems with a total quality of 40% or more, you get a GCP (Gem Cutter's Prism) back.

At the moment I'm thinking it is around 12-15%, but what do you think?

The 'normal' way to get a Q20 skill gem is to level it to L20, and then vendor it with a GCP. This gives you a skill gem of the same type back, level 1, but Q20.
It does of course take a significant amount of effort to bring the gem to L20.

The general price range for a L20 or Q20 gem seems to be around 1 EX, and GCP's seem to be 8 to 1 EX. This seem to indicate that a Q12 gem is 'worth' using 8 GCP's on to get it to Q20.

If this is correct, then the 'worth' of a quality gem of level 1 seems to be 'level-12 GCP'... with <Q13 to be used for creating GCP's...

Any opinions?

For any gem where quality is super important (e.g. Immortal Call / Ice Spear / etc), I don't vendor anything above 12% quality.

For any gem where quality is more or less irrelevant, I vendor unless it's 16%+

Lvl 1 q20 gems are about 1ex in standard so anything that I can get to q20 for less than an ex I'll keep and sell.

Question is:
Do you want to add GCPs to a gem just to maybe sell it for a bit more?
If so, upgrade any useful gem with useful quality bonus that has 15+ to 20.
(Below 15, the profit starts to get a bit low)

If you want to use it yourself, just buy a 17-18q gem quite cheap, add 2 GCP and you're fine.

With the addition of masters selling quality gems, I started to use GCPs quite frequently, even upgrading gems from 1-20%.

a) the recipe is "based" on a much higher value of GCPs than now (read: after the L20->Q20 recipe add)

b) If you have a big stash, you can keep a lot of gems while playing - and there will be q-gems also sum up. Now, some have very low quality values; and some have a very minor (or specific) use of the quality bonus in general (aura range, leech rate...). Then, you may (will) find examples of the same gem(s), with more and less quality, but not keep a 9% to use if you have also an 11% and 14% for example.
And third: if you're grinding gem xp to L20, you dont need Q'ed gems at all (beside the first levelling setup)... but some GCPs for their conversion.
All thats 'leftover' from the above, you either can try to trade, or to recipe ;)

depends on the gem, but i try to use/sell above 15%

If its a good gem with 15% keep it.

If <15% or 15% being a trash gem use for gcp recipe

Thanks for all the replies :-)