(Trying to breath new air into this thread...)
Some numbers:
The base unit price of AH-1W was $10.7 million USD. The gross purchase price is estimated at $22.8 million each.
The base unit price for AH-1Z is $14 million USD, according to Turkish sources in 1998.
The cost of refurbishing used AH-1W to AH-1Z standard is $16.5 million each, according to US military sources in 2003.
The gross unit price (including weapons, spares, training, support) for AH-64D is $56.25 million each, according to sales figure from Greek sources.
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From the figures above, I'd estimate that the gross purchase price (including munitions, spares, etc) of AH-1Z is likely to be 50% of an AH-64D.
The ROC Army wants to purchase 30 x AH-64D's. I'm interested to see a discussion in comparing 30 x AH-64D's vs. 60 AH-1Z's. What does everyone think?
To start, I'd propose (armchair general here) that the ROCA should 1) opt for 60 x AH-1Z, 2) refurbish existing fleet of 62 AH-1W to AH-1Z standard (later), and 3) refurbish existing fleet of 1970's UH-1 to UH-1Y standard via re manufacturing (rebuild from frame), plus building more from new hulls (licensed production).
The benefits include: 1) no "new" aircraft type introduced & existing support infrastructure can be used with minimal changes, 2) the ROCA would end up with a numerically larger attack helicopter fleet, 3) they'd be using the same hardware as USMC, so they can simply wait for USMC to work out all the bugs before purchasing, and have future upgrades avail as well.