I cant say its spread manipulation, but its more like having a fund for a certain fluctuation price, like for example Singapore (if my memory serves me right) has very low fuel price fluctuation due to having a certain fund that cover certain or sudden movements in crude market, meaning even if there is a sudden hike in the world market, it wont change (sudden change) the price in the local market coz there is a fund to make up for the price hike and so on and so forth, if there is a sudden decline in prices this fund gains, while prices remain the same, im not sure how it works, but in my opion, fixed spreads might have the same concept, never the less its a give and take situation between broker and trader where broker gains as well (in the long run) while trader avoid certain spread widening…
im just speaking my mind here, dont quote me on this LOL. but thats how i see it anyway.