That's because we could built the ship and the weapons ourselves back then.
Flash forward to 2014, a heavy warship would cost $1.5 billion usd. The price is high because shipbuilder wants to add profit margin and labour cost on top of the weapons and radar system. My guess is that the ship engine, radar and fire control system, sonar, anti-ship missile & anti-air system, naval guns, torpedoes, decoy launcher, other electronic stuff add up to no more than $500 million usd out of that $1.5 billion destroyer. If Viet Nam can build the hull of a destroyer and just import the weapon and radar, we can reduce the cost of a destroyer greatly.....I would say we can have a destroyer for just under $550 million usd per ship. Obtaining the modular block shipbuildiing from the Dutch is a first step. If you add more modular blocks to a corvette, it will tun into a destroyer overnight
Poor farmer's thought! You are making rice class destroyers...