2 Years ago India bought 8 P8 for $ 2.1+ billion, about 270 million per aircraft, of the shelf.
http://www.indiastrategic.in/image/img_220_mid_big.jpg
It isn't specially efficient, (Boeing will soon launch its replacement) based on a jetliner optimized for cruising at 38k ft, giving room to easily 20-30 crew members and still room left. It has redundancy typical for 2 engined aircraft, it needs big runways, can't refuel anything, can't fly slow, I haven't seen the big radar or option to engage small moving targets.
A kind of a Nimrod I guess, without the big radar and engine redundancy.
WillDAQ, a smaller, flexible, multirole platform costing 30-40% less to purchase and half to operate could easily have a 25 yr market of 300-400 IMO. The total costs of ownership would be significant lower then introducing a heritage platform.
Much of the technology / systems could be used from the A400M, CN295 MPA, A350.. The only novelty on the design would be open rotors providing 25% better fuel efficiency then todays smaller turbofans and superior low level, low speed performance.
Rolls seems to be in the lead on those, they invested a lot in them during the last 3 years. Alternatively the A400M's TP400 could offer a proven alternative.