Dishonored weapon upgrades: prices and blueprints

An upgrade's listed price covers that upgrade alone. A higher tier also needs every tier below it, and some upgrades need a blueprint first. The totals below add those costs up from the game's own prices.
Count the earlier tiers
In Dishonored 2, Pistol Reload Speed 2 costs 400 coins
and requires Pistol Reload Speed 1, which costs 200 coins.
If you own neither, the second tier takes 600 coins. The
Pistol page lists every pistol upgrade with its price and
requirements.
Dishonored prices the same path higher. Pistol Reload 2 costs 600 coins and requires Pistol Reload 1 at 300 coins: 900 coins from an unupgraded pistol.
A masterwork needs its tiers and a blueprint
Coffin Nails is a crossbow masterwork for Corvo Attano. It costs 700 coins and requires Crossbow Accuracy, Extended Bolt Range and Reload Speed, plus a Configurable Grooving. Those three upgrades cost 1,350 coins together, so the whole path is 2,050 coins and the blueprint. Coins alone cannot unlock it.
The game offers Coffin Nails or The Dealer,
not both: buying one rules out the other. Compare the pair on the
Crossbow page before you choose.
Buy the blueprint before the item
In Dishonored, Sokolov's Health Elixir costs 200 coins and requires Sokolov's Formula. The formula is a separate item, Blueprint: Sokolov's Formula, for 200 coins, so the first elixir takes 400 coins.
Mask upgrades work the same way. Mask Optics 2 (400 coins) requires Mask Optics 1 (300 coins) and Blueprint: Lens Magnification (200 coins): 900 coins for the whole path. The upgrade reference lists each shop of Dishonored and its expansions with every item's price and requirements.
Bonecharm crafting unlocks cost runes instead of coins. The bonecharm guide lists those rune purchases apart from the raw whalebone a crafted charm consumes.