Virtual currency will never be as valuable as real currency due to a few reasons.
1. The first and most important reason is that real currency can be used immediately to buy goods/services. Whereas virtual currency is limited to buying goods/services in the game world.
2. There is an intermediate step - the selling process - needed to covert virtual currency into real currency before its value can be manifested in the purchase of real goods and services. This selling process takes time and effort, and subtracts from the value of virtual currency when you are comparing virtual currency to real currency. That is why, when you are given the choice to pay for a virtual product/service in either virtual or real currency, opt to use virtual currency.