Prices are one of those things that are difficult to predict, due to their changeable nature. Who would have thought for example, that petrol prices could have gone so easily and quickly from 80p per litre to £1.22 a litre? (I remember when it was 50p a gallon - but that's a different story). OK, oak furniture prices have been rising due to the cost of fuel oil for ships and the weakness of the Pound and have increased by 10 to 20% since the beginning of 2010.
I would suggest that a typical 2 door oak wardrobe will now cost anything between £400 and £500. Anything over this and its either bespoke or you're paying for the retailer's brand. If it's much below this, check that it is actually oak and that you're dealing with a trustworthy retailer.