Well and the Su-34 too.
Anyway, i don't think the cost is any concern here, It would be the same regardles if its Su-27 or Su-30/35S.. Hell the older Flanker Su-27 migh be the costliest of them all, due to their current wear and tear.
If you put them through the Su-27SM2 program and unify them with the Su-35S in terms of avionics, engines, etc. it would not only provide a huge capability boost, but also given them a superior aircraft compared to the MiG-31BM.
If the Mig-31BM can interface the onboard comunication/network with Land based Defences as they claim, well it does have its usefull roles.
It's not useless just less useful.
Sweet. So the rest are completed, but still in debugging phase?
My mistake the first two weren't actually handed over. The pics in question were taken at NAPO, the aircraft are about to be handed over. And it seems that at least 3 more aircraft are completed and will handed over most likely before years' end. The other 5 are completed or nearly completed and will be handed over early next year.
More pics and detailed info here (in Russian):
http://militaryrussia.ru/blog/topic-8.html
There were reports a little earlier that there are some problems with the Su-34s in service right now, major problems reported were improper functioning of the radar and targeting systems. I'm currently trying to locate the link.
There are problems, these problems were well known, and are part of the reason for the mod.2011 upgrade. Part of the reason is that production is very low rate, and the plane really needs more time to iron out the creases. Given low production volumes it's taken a long time to address these issues, but they are being addressed.
It's certainly not encouraging that after nearly a squadron's worth of preserial aircraft to test and work with, and a "serial" run of 16 planes these problems still persist.