My group has just simply (for the sake of simplicity) just reduced whatever objects we find that have value to their gold value. This reduces book keeping and simplifies wealth in 4e.

However, if you want to pedantic, or show that an item is far more significant than a run of the mill gem stone there are skills in 4e that can be used for appraisal. In the Trade Goods entry in the compendium there is a section called "Buying and Selling:"

To perform either of these transactions, establish the total value of the trade goods in question. Use the major purchase column on the table in the Pocket Change entry to figure out the level of this transaction. For example, unloading a rare book worth 10,000 gp—or a forged copy of the same—would be a 15th-level transaction. Use this information with the Difficulty Class by Level table (Rules Compendium, page 126) to determine the DC to sell or buy a trade good, or to recognize or pass off a fake item.

Then make a check (usually Streetwise) to find either a buyer or a seller. Use the moderate DC for the level of the transaction in a location with a good-sized marketplace or population. Use the easy DC in major trading hubs such as the City of Brass, and the hard DC if the value of the items far exceeds the locals’ wealth. A successful check indicates that the transaction has been completed.

This is followed by a table with the prices of common items. Again, I would only use these rules occasionally, adventurers should have an idea of what the loot they find is worth, and its probably worth letting them just convert it to gold (As that is the point anyways).

So in short: Yes. Unless you want to show significance to a specific item.

Note: The RAW approach here would involve granting the players a Pouch of Platinum or similar which would allow them to automatically change gems into coins.

There's a two step process needed here.

1. Say to your players what you just said to us
2. Then mind your own business

Have they not noticed that imbalanced loot is throwing off their party balance? Or is it that they don't care? If they do not care and are having fun, it is not a problem. If they haven't noticed, then just telling them "Hey gear is important to power in Pathfinder and have you noticed that the way y'all are going about it is keeping some characters really loot poor?" should be sufficient.

For some groups, loot distribution is not some game rule thing where you must ensure adherence to "wealth by level," it's a roleplaying exercise because it's an in character activity. If they're a bunch of CN Vikings then "first with your hands on it gets it" is a perfectly viable treasure distribution practice.

I disagree with most of the other answers here that there's some burden on you to go stick customized magic into the poorer PCs' pockets until they are matched up. There's nothing wrong with personalized rewards (with in game justification) but a) that doesn't scale to someone's whole gear loadout and b) it's not healthy to do that when they are deliberately unbalancing the gear anyway - they end up getting way too much gear if you are pouring in more gear to make up for a minority of the group getting most of it.

I've been in groups where the party decides to distribute loot in a wide variety of ways - and it's not always constant in a group, it's what makes sense to the characters. In my first pirate game, for example, there was a complex ruling on who got to pick items from the loot in what order based on job title on the ship encoded into the crew's Articles. "Our raid got 10 items? Well the choice order is captain, first mate, quartermaster, master gunner, carpenter..." In my newest pirate game, there's a quartermaster who instead doles out virtual shares to all crewmates in cash and they have to "buy" specific items which are otherwise liquidated. I mentioned to them that this has a downside - if I give them high power/high gp value magic items they are inevitably liquidated for gold instead of being used for their intended purpose - but they don't care, and in the end character activities (including loot distribution) are the players' business, not the GM's.

In one campaign of ours, one player wasn't bothering to gear his caster character up well at all and the other characters sat him down had an in-character talk with him. "Dude, you're starting to not be able to affect our enemies, do you need some money for some magic or something?" In the games where groups hand out magic according to their need, it's always an in-character discussion. Because differential power levels are not a player/metagame issue, they're a character/in-game issue.

But what about encounter design being hard because of a mixed-gear-power group? It only makes designing encounters hard for you because you're inappropriately trying to compensate for player behavior. Design your encounters, and if they are too hard for the people with bad gear and they get beat up while the people with good gear skate through, it will encourage them to address the gear disparity in the interests of "everyone being able to pull their weight." You're not their mom, you don't need to "serve balance" - you are attempting to control something that's hard and frankly undesirable to control and that's what's frustrating you. Stop, and let the burden lift from your shoulders. It's not your job to compensate for every decision, good and bad, your special little snowflakes make.