In the first instance there are too many types of coins: Platinum, Gold, Silver and Copper. Copper is useless. Even at level 1 everything costs silver or gold and by level 3 I routinely buy things that cost 100's or 1000's of gold.
The next problem is that the multiplier between tiers of coin is only 10 as opposed to the more usual 100. I am sure I will eventually get used to this but even after two weeks playing I still need to remind myself that 50 silver is equal in value to 5 gold.
The NPCs vendors don't help the situation by routinely ignoring platinum when quoting prices. The ingredients to inscribe a level 2 spell for example are quoted at 420 gold instead of 42 platinum.
Finally and perhaps the most confusing thing of all is that your purse does not automatically convert coins to the largest denomination. For example my purse might contain: 21 Platinum, 194 Gold, 211 Silver and 384 Copper. Can I afford to buy level 2 inscription materials which are quoted at 420 gold?
Is this some kind of slavish adherence to the AD&D ruleset? I don't know but how hard can it be to implement a simple algorithm to add up the coins in your purse?
By the way the answer is yes. I can afford the inscription materials and I will have 0 platinum, 8 gold, 9 silver and 4 copper left over.