It would be great if we could set pricing in SDBs to 'per use of wear' for items such as tools, powders and potions. That way, you know exactly what you are paying for and aren't taking the risk of paying for what you think is a full jar of EHSP only to find there is only one use left in it. I know it may be a bit tricky due to the nature of SDBs as one may try to buy 5 uses of wear of EHSP but there are 2 jars in the SDB - one with 2 uses and one with 4 but perhaps the number typed in to the 'buy how many' window could change to the nearest possible number similar to what happens in windows when you try to make more of something than you have enough ingredients for.
I'd also love to be able to combine 2 powders or potions if the amount of uses left meant that both would fit into one.