Ewan has it exactly right. The starting point was the "chassis" table in Book 8: Robots.
Code:
Volume Weight Price
(L) (kg) (Cr)
5 0.5 1500
10 1.0 2500
20 2.0 4000
50 5.0 7500
80 8.0 9500
100 10.0 1000
150 15.0 1500
200 20.0 2000
350 35.0 2500
500 50.0 3000
750 75.0 3500
1000 100.0 4000
2000 200.0 5000
3000 300.0 6000
For all volumes under 100 litres, if you divide the price by 10, you get the following.
Code:
[FONT="Courier New"]Volume Weight Price
(L) (kg) (Cr)
5 0.5 150
10 1.0 250
20 2.0 400
50 5.0 750
80 8.0 950
100 10.0 1000
150 15.0 1500
200 20.0 2000
350 35.0 2500
500 50.0 3000
750 75.0 3500
1000 100.0 4000
2000 200.0 5000
3000 300.0 6000[/FONT]
This is a progression that makes more sense - smaller hull sizes need less work and materials to make. Note that the progression is not linear, and the price per litre of hull increases as the size gets smaller.
Rob Prior's table in his text was:
Code:
[FONT="Courier New"]
Hull Size Volume Weight Price
(UCP) (L) (kg) (Cr)
--------------------------------
0.00035 5 0.5 75
0.0007 10 1.0 100
0.0014 20 2.0 200
0.0035 50 5.0 300
0.0056 80 8.0 350
0.0070 100 10.0 400[/FONT]
If you compare the listing for the 500, 750 and 1000 litre hulls in the MegaTraveller Referee's Manual, you get the following comparison
Code:
[FONT="Courier New"] ---Book 8--- ---MegaTrav---
Volume Weight Price Weight Price
(L) (kg) (Cr) (kg) (Cr)
500 50.0 3000 50 1200
750 75.0 3500 75 1400
1000 100.0 4000 100 1600
[/FONT]
That is to say, same weight but Book 8 lists the chassis at 2.5 times the price for robots. So I divided all the prices in Book 8 (after the initial dividing by 10 for the smaller hull sizes), which gave me this.
Code:
[FONT="Courier New"]Volume Weight Price
(L) (kg) (Cr)
5 0.5 60
10 1.0 100
20 2.0 160
50 5.0 300
80 8.0 380
100 10.0 400
150 15.0 600
200 20.0 800
350 35.0 1000
500 50.0 1200
750 75.0 1400
1000 100.0 1600
2000 200.0 2000
3000 300.0 2400[/FONT]
I then added in a few hull weights / prices, using the MegaTraveller extrapolation rule. I agree Tom, this rule results in some anomalies - depending on which hull size one rounds to, a slightly smaller hull could be more expensive than a larger one!
But I decided not to change this situation. I did extensive charts with plots of a cost-per-litre curve and tried to get a curve of best fit based around a hyperbole to derive a formula for any given size. Then late one night staring at the screen I realised - this is going to make less than Cr100 difference to nearly all the robot designs in my spreadsheet. Why am I bothering? Getting rid of the anomalies is not worth the effort, and after all, there are just some quirks in MegaTraveller. It's not going to interfere in game play.
Having said all of that, I'd be interested to see anything you come up with that improves the hull size cost calculations as it was a puzzle that had me going for a while.