Pocket Pots O' Gold
Has anyone actually looked at the size of those gold pieces? Just think of the Spanish Dubloons from the sunken treasure films you've seen. How many of those do you actually think can fit in one pouch? Five? Ten? Twenty?
I can hear many of you screaming now: "But I don't want to deal with that Encumbrance stuff!" Patience, please.
I am in no way suggesting that you should carefully weigh each coin and keep detailed records every time you buy something, share gold (gasp!) with party members, get robbed, visit the... ahem. Onward. For most of the people that I've played with that would never fly. We play to enjoy ourselves and the characters are the foremost concern. So no, I'm definitely not suggesting that.
The easiest, and most boring, solution would be to just use some common sense. "You've got HOW many gp's with you?!?" Make your players keep their gold someplace, or transfer it into gems. Gems are much more portable, but would require a money-changer or jeweler to get cold hard cash. This gives you, the GM, the opportunity to correct some mistakes you might have made earlier: handing out too much or too little money. Money-changers will always take a cut (5% is pretty decent, but 10%, or more, could be pretty common.) Jewelers will only pay about 1/2 to 1/3 what they think they could get from the gem. Talk about cutting down the money supply!
Don't make these the only ways your characters can use the gems, though. They would stop using gems, and that would defeat the whole purpose! Many merchants can, or have someone who can, appraise the gems and use them for trade.
Make things more interesting. Don't just hand out tons of money. Feel free to let your players find "paper money" in treasure. IOU's can be great sources of adventure, or bank-notes. Trying to find the proper bank to cash it at, or angling for a reward by returning it to the owner. Pieces of art can be fun, too. They are always worth only what the buyer is willing to pay. Trying to find out the history of a piece to find the best buyer is a fun side plot if used sparingly.
Note that this doesn't just apply to money. Backpacks are often packed beyond reason. Most of us always have at least 50' of rope with us, a handful of torches, a grappling hook, a number of (fragile!) flasks of oil, a change of cloths, a tent, a bedroll... Need I really go on? Remember, ropes back then were not the 1/4" nylon rope that we think of today. It was often 1/2", 1" or larger in diameter. A 50' roll of rope would look like something you'd see on a dock for anchoring the ships. A backpack with that much stuff in it would weigh down a couple of pack-mules!
Find creative ways to keep your players honest. Never, and I repeat NEVER! tell your characters point blank that they can not do that! Let them try carrying all that stuff in their packs. Think of how much weight they are carrying. Boy (yawn) they must be getting exhausted! Oh, look! A group of bandit, vorpal-bunnies, and him such an easy target! What do you mean you don't deserve a -100 penalty? Yea, I know its just a d20!
There are all sorts of possibilities. So go out, read books on history or novels in the genre you're dealing with. Always keep an eye out for these sorts of problems and their respective solutions.
Most importantly, though, whether as a player or GM -- use your head! If it seems like an awful lot of stuff, it probably is. Force them to get rid of it, or change in shape, through gentle persuasion.
Enjoy your brains!