Honestly D&Ds gold pricing has always bugged me, even just calling it a gp rather than a Crown or Mark also bugs me. I much prefer Warhammer 1e or 4e, based on historical pricing. 1 Crown (GC) = 20 Shillings (s) = 240 Pence (d). With one pence buying a cheap beer. A pence would still be made out of silver though, just less of it than a shilling. A copper farthing would be 1/4 of a pence.
It always seems ridiculous when gp gets thrown around like dollar bills, especially with the inflated prices for things like armor. A 1500 gp for plate? A gp should be something that a commoner will likely never see in their life times, mostly used for international trade, taxation, ect.
If wanting to use a decimal system, to make it easier to remember. I like the way Righteous Blood Ruthless Blades (based on China) does it: 100 coins (copper) = 1 silver coin, 10 silver coins = 1 gold coin. All transactions are just in "coin" the copper denomination, larger sized currency would just be easier to carry or be a part of loot.
^2