It also depends on what you mean by 'fair'.
The 'right' price for any seat is what the punter is prepared to pay. Put it too high and you don't get the booking, put it too low and you spill revenue. As Paxboy says this 'right' price is dynamic and is likely to change frequently, up and down, based on a number of factors.
In the EU it is illegal to price differently based on the location or nationality of the purchaser. (i.e. A London to Paris ticket must be the same price (at the same moment in time) regardless of where in the EU it is purchased.)
You also have airlines price at a level that will drive customers to them to purchase related products. Baggage, seat selection, boarding priority, food and drink costs can easily exceed the ticket price.
It is impossible, with most airlines, to know what the total price of your journey is going to be. But then again you get what you pay for, and with a little planning you can reduce your costs significantly.
If you suspect that an airline is targeting you, there are ways around that. Use a VPN, for example.