bronze was considered to be better than iron but they used what they could get. bronze was hard to come by but held up better than iron did. until a better way of making iron was invented bronze guns were stronger.
yes most ships carried money aboard for buying supplies,food,water,barrels,oil for lamps,or whatever. some were used to transport supplies to remote bases and money for crown transactions, buying land paying rent on housing for troops, buying neccessary sundries for armies/navies, paying laborers building forts/housing for troops. and for the building of ships at the remote base.
anything used to do anything was carried on ships incuding cattle,arms,cannons for forts,cooking/eating utensils,household supplies,uniforms,swords,gunpowder,building materials/tools,heating/cooking stoves, medical supplies/instruments,nails,spikes,hammers,saws,axes,adz's,barreled grain, meat, and just about anything.
as far as what is something worth, it depends on how rare it is and how much is there. remember smuggling was rampant so anything goes. if the british considered the cargo expensive it might still be or not. I doubt 100 barrels of rotten pickled beef is going to be worth anything but a general cargo of rare items or a payment or equipment or weapons or even building supplies might be.
after watching the antiques road show, it has shown me a few things. the rarer it is the more it is worth, and some things, that I would not even bother with could be priceless. I saw a lady pay $8.00 dollars for a $250,000.00 clock at a yard sale and it looked like trash to me. all it really takes is 1 item to pay off and you're set.
I hope this helps, don't be afraid to ask me anything if you want.