There are a couple different challenges faced here, when it comes to ideas of money, exchange, and terminology going that far back in Ancient Egypt. Unfortunately, I don't think there's an easy answer, but here are some things to consider in your design process.

The Deben: While its definition would change to be far more consistent later in Egypt's history, the deben in the early old kingdom should not be looked at as either a unit of currency like a dollar, nor as a specific weight like an ounce. Rather, a deben was a specific weight of a specific thing. Something wasn't worth "five debens" - it was worth "five debens of..." something specific. A deben of copper did not weigh the same as a deben of gold, and a deben of each did not have the same value. Think of the word deben as meaning something like "unit." One unit of copper weighed the same and was worth the same as another unit of copper, but one unit of silver both weighed and was worth something different.

Money: Money, in the modern sense, did not exist. Coinage wouldn't turn up until around 2000 years after the time you're looking at. Values could be compared for barter purposes using the deben system, but that was more a means of establishing value than an actual system of exchange. If you were to purchase 5 sacks of grain, you might trade for it 3 copper pots, several linen garments, and some oil. Both sides might be said to be worth a certain amount, let's say 2 debens of silver, but no actual silver would be exchanged. The reason the weight matters is because it is conceptually still a real thing. Something has the value of a certain specific weight of a precious metal, and that precious metal has a certain value based on its weight. To say something is worth as much as 50 grams of silver is to give it a value, even if you never use actual silver in the exchange.

Wages and the Economy: The economy was centralized to a very high degree, with literally everything in the country being the property of the pharoah, who doled out necessities like food, clothing, and holy oils via his officials in exchange for work done. Workers and soldiers weren't paid in something meant to be exchanged - they received what they needed to live. They received their food from their pay clerk, or grew it themselves. They received their clothing from their job, or they made it themselves. They were assigned a house at their work location, or they built one themselves. High officials, often royal relatives, could control vast areas of land and receive the products from those working those lands, but even then the lands would revert to the pharaoh upon death for distribution to a new official. When it comes to the question of "could X amount of something buy a sword," I think the more important question is "could you find a sword for sale?" Such things would be made to the order of the government, for distribution by the government, to people who needed one for their work on behalf of the government.

Technology: One extra thing to keep in mind, since you're looking at a role playing game setting, is exactly how long ago this is technologically. While your target date is within the bronze age, plain copper was far more common until later in the timeline. Iron was practically unheard of, consisting almost exclusively of a few royal objects crafted from iron meteorites found in the desert. Work was done with tools of stone, wood, and copper, using sand as an abrasive for cutting and polishing. Neither daily life, nor the economic system, was conducive to freely-wandering mercenary types trying to make it on their own.

Sources:
"The Oxford History of Ancient Egypt" by Ian Shaw
"Everyday Life in Ancient Egypt" by Lionel Casson

NB: If you're interested in RPGs themed off Ancient Egypt, it may be worth taking a look at the 1983 boxed set from Palladium called "The Valley of the Pharaohs" (not to be confused with the unrelated 2006 board game of a similar name). It is set in the New Kingdom, so the situation is much different, but some elements may be transferable or serve as inspiration.