The biggest problem I've run into was arms and armor.
This is because in 1e AD&D there were two economies - a semi-realistic silver economy based on Gygax's historical research and simulations that NPCs used and an unrealistic economy based on gamist needs and balance and a desire for huge piles of fantasy treasure that PCs used. This inherently creates the problem you see with the crafting.
Incidentally, Gygax tried to both explain and justify the two economies by saying that the dungeon/PC economy was a microeconomy that worked similar to the economy of the Klondike gold rush, but neither he nor any subsequent author was consistent in applying that logic. Gygax new very well that the prices of arms and armor in the 1e Player's Handbook were not realistic, he just didn't expect this to become a problem in an easy come easy go dungeon delve environment that was what he was playing at the time.
So let's say that a smith expects to make about 3 s.p. per day, and it takes him say three days to make a sword. That means he expects to sell that sword at a profit of like 9 s.p., and on the rule that two thirds of anything is labor it costs him say 6 s.p. in materials like coal and iron and in overehead to do the work. So, this now is consistent. A sword costs like 15 s.p., takes three days to make, and requires a reasonably skilled smith. Or you could do this with g.p. and that would be fine too just as long as you are consistent about applying the concept (gold economy or silver economy).
So part of the problem here may be your conversion rates. The smith is making 3 s.p. a day after paying his expenses, and working say 300 days a year. If a s.p. (or g.p. in a gold economy) is worth about $75, then the smith is making about $67,500 a year. Everything he buys is handcrafted goods, so he doesn't live nearly as well on that money as a modern person because almost everything (except those things modern people by that is hand made) is more expensive. But within the society he's comfortably middle class.
Things though get weird though when you start applying concepts like "masterwork". Suppose to make a masterwork sword you have to have a master craftsman who wants 5 s.p. a day. What's going on to make the sword worth 20 times as much? Does it take 20 times as long to make? Does it take ingredients that are 20 times as expensive? No, what's really going on is that that the price was pulled out of the air for balance reasons - a gamist economy not a simulation economy. Maybe it takes twice and long and has twice as costly of inputs, but that's still six days at 5 s.p. a day plus 12 s.p. of inputs for like 42 s.p. compared to 15 s.p. You can make the sword more expensive by making it more ornate and showing with decorations, but it won't make it a better sword except for walking around court like you belong there.
And that master smith is making say $112,500 in equivalent wages and not $1.2+ million in equivalent wages or whatever would be implied by making swords 20 times more expensive.
When the ranger wants to buy a suit of studded leather armor who does he go see?
Of course, as long as we are talking realism, studded leather armor doesn't exist. If he's going for something like that he's going for brigandine or "coat of plates". But OK, sure the question you really need to be asking is if a PC buys leather armor and some bits of metal, how fast can he turn 10 gp investment into 45gp worth of armor by crafting his own studs? Can he effectively get a wage of 35 gp a day by making his own studs and mounting them on the leather (leaving aside how bad of an idea this is in real life)? Or at least say 10 gp a day? Can the PC's manipulate the gamist price list to create unreasonably high living wages in a short time in order to roll that easily earned money into some large material advantage? This is a trivial example of that. Longbows are probably better examples.
Better yet, if you are on the gold piece economy but NPCs are on a silver piece economy, can you pull money from the dungeon to then hire basically all the unskilled labor in society by increasing their wages because the exchange rate between gold and labor is so good? Can you then instead of being "Indiana Jones" be Belloq and just hire laborers to dig up Acererak's tomb, by passing all the traps and reducing the Tomb of Horrors to just a labor management and logistics problem with an occasional fight against wandering monsters seeking to eat your labor force?