I've thought sincerely about including all the prices on these lists, but honestly it wouldn't do the reader any good. The prices are calculated and would not be the same from place to place anyway ... wooden articles being more expensive in desert areas, for instance. Besides, I know that most players would rather just assign their own prices to things, on the basis of wanting to keep said object out of the players hands by making it very expensive.
Lately to get the prices I use I've been breaking the objects down into smaller and smaller bits in order to assign a price. For example, the catapult is rated according to the amount of wood, ironmongery and rope needed to create the object. This means that objects which are created from a large number of different materials tend to keep a steadier price - as one material may increase in value as one travels, another material may decrease.
The reader will note that the trebuchet and the catapults are relatively cheap. I think this is more accurate than earlier efforts I've made which have resulted in these things being expensive. By decreasing the iron pieces and nails (I found some self-made siege device webpages that convinced me the percentage of the whole project would be smaller), the price dropped - wood, particularly in Europe, is cheap.
If the trebuchet is considered, yes, the price is low ... but consider the steady price of paying artillerists to maintain and fire it, or the sixty wagons necessary, with drivers and oxen, to move it once disassembled. The initial price might be doable, but a party would soon find it wasn't worth the effort. Oh, incidentally, the reason why the counterweight is not included is because it's size depends upon how much you're interested in throwing.
Black powder was discussed in the comment section of Apothecary's Equipment a couple of posts ago, so I can let it go. The smoke bomb is exactly as it says - not particularly lethal, and fairly reliable, though useless in on a windy day.
The land mine has been described on this blog before.
One thing I love doing, which my players really, really hate, is the continued use of the Imperial system. Kind of funny, really, as it makes more work for me too, but somehow inherently the metric system doesn't sound right for use with D&D. I'm not an anti-metric system fanatic, but if the world is supposed to take place in the 17th century, I insist upon 17th century units of measurement. Thus, a 'stone' is 16 lbs ... for those readers who may not know.
The rest, I think, is self explanatory.