China and India do pay full price and cash for oil - it's one of the biggest expenditures of government. India doesn't really make advanced weaponry (just starting to do so now - definitely nothing sold) - it obtains weapons from Israel, France, and Russia. China makes weaponry, but it isn't great.
Actually, Asian countries (China, India, Japan, and the rest) pay *higher* prices for oil - there's a small surcharge (well, small in percentage terms) imposed on oil sales to Asian countries - I'm not sure of the reasoning behind it but it definitely exists.
Thanks. China has weapons to sell and nuclear bomb making technology. Also missile technology. Plus the Chinese stooge North Korea has been selling missiles to Iran and probably missile technology