You're missing the fact that the there are actually a huge amount of fluctuating coins in the market. Since gifting came and then coin trade, it has given people a major motivation to donate: easy access to gold and items. Coins are being used as a commodity, another currency, and a trade good.
Devaluation doesn't just limit to physical item but also currency. For example the euro and the dollar is at around 1.3$ per Ôé¼ recently. This is a major devaluation of the euro since a few months ago when it was close to 2$ a Ôé¼. Currencies also have a supply (excluding the govt printing more money) and demand. And when a currency is more demanded its value increases in terms of everything (items costing more for example), vice versa when that currency loses its demand for various reasons it's devalued (items costs less to buy).
Anything else confusing you?
What I'm trying to argue here is: the op wanted a fixed exchange rate between the gold and coin. And fixed exchange rate, as proven by the great depression of the 30s, to be ineffective in terms of the economy. Also a fixed exchange rate cannot be determined by a minor factor of the market, only by the government (molten staff putting a maximum cap on hope much gold can be entered per entry). And a cap (price ceiling, google it) would cause what we call a shortage of supply and privately illegal trade would occur for buyers who has excess resource to spend (illegal gifting for gold using various resources in this situation). This would heavily reduce incentive to donate in our situation (low supply) while demand significantly increases.
Basic supply and demand.
Now in terms of your argument that items are for sale for coins, well you misunderstand the origins and basic concept of the economy/market. Basically coin is Also an item and a commodity that is used to trade for other items. Same with any kind of currency in the world. A printed resource used for trading. Before dollar standard (arguably the gold-exchange standard also), gold was used as a main commodity and money was basically bank note of saying how much gold you have in the bank.
Phew .-. Typing and editing this from an iPod touch is a lot of work...
I should be gifted with coins for writing all this xD
