Yes i experience as well

when last April, i went to Doha to Chennai return, ticket costed me QRS.2650 but when my friend came from Abu Dhabi joined me in Doha in the same flight he paid only QRS.1600 return, it is really very strange, i ask the Qatar Airways office why the cost is so much difference, but they told me readymade answer " WE DON'T KNOW" !!!