I was thinking that it might be nice if the money is power spell (MIP) was
effected by the type of coin being carried.
If the mip ratio (exp/gp) was improved by a bit more than the typical 5-7%
loss/markup involved in going from gold to high coins, using high coins could
become an option that could be advantages, thereby increasing the use for
the exchange money skill. Any little additional exp gained via this method,
would only be a little bonus and it would be earnt by going to the trouble of
using high coins.
Such a change would also add a bit of flavour to the spell. Perhaps the use
of highcoins could have a slightly different effect, say maybe a larger
overall
range of ratio, or maybe some change of +luck or something.