Switching between 1x and 100x magnification also has its downsides for anything slightly above one diluted pool worth of mana.
At some point I had an idea for a somewhat radically different way to show it: The cost indicator is split into two parts, the bar on the right and one or more pools on the left. Amounts below one diluted pool just display a partially filled diluted pool and the bar that indicates how much of a diluted pool it is. If it's somewhere in the range of, say, up to 5 diluted pools, you get a number of full diluted pool icons and a partially-filled one for the mana bar that shows the remainder. (For something like a mana diamond, where it's exactly a multiple of diluted pools, the bar is full and the full pools part contains one fewer than the actual multiple, since that last one is represented by the bar.)
When the amount exceeds a reasonable number of diluted pools, the display switches to showing it as regular pools. I guess a special case would be exactly a full pool + 1 mana, which is allowed as the maximum cost for mana infusion to only do that in creative pools. Other lower or higher amounts (e.g. terra plate recipes requiring a couple of pools worth) just use the same mechanism as the diluted pool approach above.
I haven't tried mocking up this approach to see if it can be presented in a reasonable way, but maybe I should do that to see if it's viable.