I'd say the PAF wants a fighter, but external factors -- primarily economic -- are genuine constraints. For a Su-35 sale to work the Russians will need to park the equivalent foreign currency into Pakistan via counter-trade, FDI and other measures.
They're willing to look at it in general (e.g. see the
barter deal with Indonesia or Rosoboronexport studying
trade in local currencies), so it's a plausible outcome.
However, external factors -- i.e. how far Washington pulls India away from Russia -- and some internal ones -- like medium-term economic promise -- are going to matter in the end. Plus for the PKR to matter to the Russians, we'll need to make something of value to them.
FYI ... Russian Helicopters is supposedly nearing Kazan Ansat helicopter sales to the Pakistani private-sector (
link). I suspect the local currency factor is kicking-in, but with enough customers of the helicopter in Pakistan, we might just see the Russians invest in MRO sites (which they'll own) to service those users.
