We’re giving some thought to some changes and improvements to the cost efficiency feature.
People have asked for something similar to what you suggest, so we might add something like that. I think we’ll make it a bit more flexible though… and let people enter in any amount of currency so that they can plan ahead.
Given the relatively high cost of obtaining upgrade currencies, it’s usually a good idea to plan ahead at least a little bit. It also gives people a way to get a ranking even if they don’t have any currencies on them at the moment.
That said, as a player I still have concerns with this kind of ranking. An example helps to illustrate:
Say that I have 5 items that can be upgraded. They are all rank 1 right now, and they can all be upgraded to rank 8. Most upgrades switch from one currency to another going from rank 4 to 5, so you really have to break each item into two different upgrades:
1->4 (costs crest type 1 and valorstone amount X)
4->8 (costs crest type 2 and valorstone amount Y)
Thus you have 10 potential “upgrades”, 2 for each item.
Note that “partial” upgrades, e.g. only taking an item from 1->2 instead of all the way to 4, are going to be of essentially the same efficiency as the “full” upgrade. Thus if upgrading item A from 1->2 is your best option right now, your next best option will almost always be taking that same item from 2->3, then 3->4. In other words, when possible, you want to “finish” one item (to the point where the cost changes, at which point its efficiency changes and you re-evaluate).
Say that my most efficient upgrade is taking item A from 1->4. I have enough currency to do that, so I do it. Then my next best upgrade is taking item B from 1->4. I do that too. Then my next best upgrade is taking item A from 4->8, so I do that.
Now I have just a little bit of currency left. I don’t have enough to do my next-best upgrade, which is taking item B from 4->8. I don’t even have enough to take it from 4->5. But I do have enough to do a partial upgrade of my next best upgrade: I can take item C from 1->2. So I do that, and now I’m out of currency.
I would argue that last partial upgrade, taking item C from 1->2, is a waste. I would be better off saving that and using it next week (or whenever I get more currency) to continue upgrading item B instead.
Hopefully that example illustrates why I was hesitant to do this kind of ranking. By putting a hard cap on the amount of currency, you end up spreading your upgrades around to use up as much of the currency as possible… when often you would be better off saving it up to do higher efficiency upgrades next week or whenever you get new gear or more currency.