I think this is true of most places in the world. It's probably a bit worse here.
If you 'act the tourist' (a little uncertain, hesitant, ostensibly not in the know regarding how it works here, etc.), few would have the scruples to not take advantage of that.
If you're Caucasian, it could be worse...for some reason it is assumed that 'white people' have more to spare and are ripe for the ripping-off. Sad but true.

Act confident and in the know (I do it even in taxis, though I haven't a clue about the routes yet), hold your own, be assertive and never hesitate to ask why. I'm a female newbie to Qatar, too.