By "infinite" I mean that the "lost money" from using the wand will be given back to you in future in the treasure the GM hands out to keep you at wealth by level.
IN Theory:
If you have several permanent magical items you'll only get the little bit you need to keep at wealth by level as you level up.
However lets say you have a charged item (a wand in this case). As you use the wand up you have less wealth since it's value goes down per charge used. Once the wand is used up you are effectively down that much in your wealth by level -- which means the GM now needs to give you another source of wealth in addition to what you would normally get to keep you at "wealth by level".
That's the whole idea behind wealth by level -- that no matter what form or how you use it you'll still end up at the equilibrium point suggested. Yes your magical sword might be broke... but the GM is expected to get you something to keep your wealth where it needs to be -- In fact if you go "over" wealth by level you really shouldn't expect any treasure for a while -- you have to "even out" either by using stuff up, or by gaining exp/levels until you are back at even. This is easily shown in the LoF AP actually in the way it gets you ahead in some places before ditching you in the middle of nowhere so that you can't replenish or immediately use the resources you find in the next adventure.
Now on to the specific wands:
The extended acid arrow is indeed for the concentration checks, however as an on going source of damage it's good for most types of regeneration too (since it will negate it each round)... indeed 2d4 over 10 rounds is 20d4 which isn't bad off a wand that doesn't have to worry about save throws or spell resistance (at 3rd level too). Does it take time? Yes, but that time can be used to your advantage of course (see the concentration checks or hit and run tactics that you referenced).
Pearls of power are nice, but again reference the "in theory" above. That third level pearl is going to be...
That's just plain wrong. As a DM, I'd give out treasure/gold at a reasonable rate and let the chips fall how they may. If a PC spends his money wisely and comes out slightly more powerful than he should be at level, then his job is somewhat easier, and I am ok with that. If the PC makes unwise decisions that's ok by me as well, his life will get more difficult.
While I might make exceptions to that in rare circumstances (say the party is caught in a Morts Disjucntion), in general, no way. I'd be even less likely to do it for just one character who used his money poorly, expecting me to replace the money squandered...