Where can you buy a sword that has 50 +1 charges? How much do these cost?
For the sake of argument, let's look at the lifespan of a +1 weapon:
Let's say a +1 weapon is acquired at third level and used until sixth. In general you have 13 encounters between leveling, so that's almost 40 encounters for the weapon's lifespan.
The weapon generally costs 2300 gp. It can be sold later for half value, so you are actually only spending 1150 gp.
So let's say the fighter had to pay. If it's per encounter he is paying 29 gp per encounter. If it's per swing (let's say 150) it's 8 gp per activation. I would say it should be per swing, because unlike an item like a wand of magic weapon the fighter doesn't have to waste an action activating the item.
The cost of healing from wand charges can be considerably higher per encounter, especially if the party is large. On average each encounter should consume about 20% of the party's hit points. Between 3rd-5th level, with four members in your party that's probably 20 hp, or 4 charges of a wand (60 gp). With six members in your party that's probably 75-90 gp per encounter.
Really? Taking a look at the adventure paths from Paizo and WotC, there are very few opportunities for the DM (from the raw module alone) to sunder weapons and armor. There are plenty of opportunities, on the other hand, to make the party chew through wands of cure light wounds. In the campaign I'm currently in we're on our sixth wand already and we're only level 4.