I am finding the same issue with some exchanges as other members reported before me.
In this example I checked rates on OrangeFren and Swapuz exchange gave me the best rates,
but when I was redirected to Swapuz website I found different rates, and I refreshed page several times to confirm.


It's interesting that sometimes I am getting better rates than it was reported on OrangeFren wesbite.
For example this happened with Hellex exchange, I selected swap from BTC to XMR.


So maybe there is some issue with OrangeFren, not with exchanges trying to trick anyone.
Thanks for the findings but for me i believe these inconsistencies are usually due to the aggregator OrangeFren data refresh speed and the fast-moving nature of crypto prices, rather than intentional manipulation by the exchanges themselves.
What i can say is always double-check rates directly on the exact exchange site before making a trade to ensure you’re getting the best deal.