"Rabbi Chisda said: I wash my hands with an abundance of water and I am granted an abundance of goodness" (Shabbat 62b).
There's also a story from the Zohar with Rabbi Elazar Ben Shimon, Rabbi Yoezer and Rashbi that I've heard that associates this abundance and goodness with wealth (does anyone have the source?).
Many if not the majority of times we do netilat yadayim, we do so using someone else's water. Whether it be our shabbat host, or our shul or yeshiva, the point is, someone else is paying for the water. It's common for water rates to be set by usage by volume.
In some countries where yidden live, as well as in Talmudic times, water is/was likely in many cases far more expensive/labour intensive than it is compared to nowadays, in first world countries with indoor plumbing and abundant cheap clean water (Hodu laShem ki tov). Even in first world countries, even if it is less than a pruta, there is what to consider1. It might be ok if it is generally people don't mind and it is less than a pruta2, but it is still better not to3 (which would certainly be something that can affect the fulfilment of a segula)
Therefore, it's quite ironic to consider taking more water than necessary to secure a segula for wealth when someone else is paying for that water!
Is there any discussion of this? Does this segula only apply when it's your own water? I believe the story in the Zohar might imply that (i.e. the reward for using extra water to keep the halachot as meticulously as possible, even though it costs you more money, your reward is, poetically, wealth). Or perhaps this segula will extend to our host and we should do so for their sake? Or perhaps we are simply to assume that our host would wish us to use more water in order to guarantee we fulfil the halacha meticulously, segula aside.
Perhaps, perhaps, perhaps, does anyone discuss this?
1 Shulchan Aruch CM 348:1, Kitzur Shulchan Aruch 182:1
2 Shulchan Aruch CM 359:1, Kitzur Shulchan Aruch CM 182:1
3 Rama 359:1