Ok, the lance is just an example where the item tonnage varies incrementally by the unit tonnage, but the cost varies by a different increment. On pg. 405 of TO, the weight of a lance is the (unit tonnage)/20, rounding up to the nearest half-ton. So a 35-ton mech and a 40-ton mech would both use a 2-ton lance, thus it would seem that you could salvage a lance from a 35-tonner for a 40-tonner. However, the cost of a lance is given by 150 * (unit tonnage), so the 2-ton lance for the 35-tonner would cost 5250, while the 2-ton lance for the 40 toner would cost 6000. Does the difference in cost mean that these two 2-ton lances are not interchangeable?
Note that there are quite a few items in this situation where the item tonnage is the same, but the price is different.
