Cost of M113
In 1977, a batch of 1200 M113A1 cost the U.S Army $73,250 per unit. As the value of the U.S. Dollar and the Imperial Credit at the time were the same, that would put the price of one of those M113A1 at 73,250 Credits.
I have not yet located the price of the first batch of 32 M113 delivered in 1960, but I can make an educated estimate. The inflation factor from 1960 to 1977 is exactly 2. Given the very large number made by 1977, including license production overseas, the cost per unit for volume production should have dropped considerably. Richard Ogorkiewisc in his book Armoured Forces gives the reduction in cost for a production run of 2,000 vehicles of a factor between 3 and 4. As by 1979, somewhere in excess of 70,000 M113s and variants had been produced, volume production should have dropped the per unit cost by at least a factor of 4, and possibly 5 compared to the initial per unit cost. The first vehicle run also use gasoline verses Diesel engines, which also would have reduced costs. So, taking the $73,250 per unit is 1977, dividing by 2 and multiplying by 5, one gets $183,125 per unit for the first units.
For the current cost, there is a range of values. The inflation rate from January of 1977 to January of 2017 is a factor of 4.15 from the Bureau of Labor Statistics.. The would make the M113 cost $303,987.50.
If you use Ogorkiewisc rule of thumb for WW2 armored vehicles at costing about a Dollar per pound, and the inflation factor from 1944 to 2017 at almost exactly 14, that would make the initial 19,755 pound vehicle cost about $276,570. Hmm, not too far from the above figure, but both are based on the inflation factor, so not truly independent.
If I use the price of gold circa 1978 at about $200 per ounces, close to the yearly average, with the price of an ounce of gold in Imperial Credits also being 200, verses the $1200 per ounce gold as been sitting around of late, then the price would increase by 6 over the $73,250 or $439,500. That seems a bit high, but if you plug in the Imperial Credit being worth 2 Dollars, that would drop it it 219,750 Credits. That feels a bit more accurate with volume production.
Now, if you were going to produce a small number of the vehicles, then the $439,500 might not be too far off of the mark, as the 1977 value was for a very large number of vehicles. Then it might be best to use a straight Credit per Dollar exchange rate, and price the vehicle at 439,500 Credits. A oneoff custombuilt vehicle should run at least twice that.
There are a couple of other ways of looking at possible costs that I can think of, but those are a tad esoteric. I was looking for a fairly simple way to assess costs. It looks like, depending on the volume of production, either the cost per pound would work for not fully known costs or plugging in the inflation factor where the cost is known. For lower production rates, the change in value in gold might work best.
