According to the standard reading of masochism, the masochist, like everyone, also looks for pleasure; his problem is that, because of the internalized superego, he has to pay for his access to pleasure with the pain, to pacify the oppressive agency which finds pleasure intolerable.
For Deleuze, on the contrary, the masochist chooses pain in order to dissolve the pseudo-link of desire with pleasure as its extrinsic measure.
Pleasure is in no way something that can only be reached via the detour of pain, but that which has to be delayed to the maximum since it is something which interrupts the continuous process of the positive desire.
There is an immanent joy of desire, as if desire fills itself with itself and its contemplations, and which does not imply any lack, any impossibility.
'Organs without Bodies: On Deleuze and Consequences' by Slavoj Zizek
https://www.amazon.com/dp/B0081YW5KK