Concept Number 1: Cash coming in
There needs to be a way to get money into an economy. An economy that is shrinking in circulation isn’t always good. For people to make money, there must be a money source. This is mining, silver grinding, sieges and siege regions, trade contracts, and whatever else I've missed.

Concept Number 2: Cash coming out
We can't just have endless cash coming into the system. The more cash in the system, the easier it is to buy, and the easier it is to buy, the more likely prices are to rise. Alternatively, upkeeping towns (which is really the only fixed sense of expense) becomes easier. Therefore, money sinks like Upkeep and AH taxes exist to remove money from the economy.

Scale of progression
There is probably a business term for this, but the more capital acquired, the easier it becomes to accumulate more capital. A person with 10k versus a person with 50k — if you ask them both to make 5k in a day, it's quite likely the person with 50k will be more than able to make this.

Both CCNet and IRL require investments to do this. IRL, I might invest in a bunch of products and then attempt to sell at a profit, or I might buy a property or company. In CCNet, you invest in silver grinding. Once you arrive on this ladder, it becomes easier to make more money.

A Faux comparison
The issue with silver grinding is that once you have a formidable setup, and you can use a portion of the money you produce to buy the energy, you have essentially found a surefire way to turn time into money. Unlike mining, where duct tape is constantly needed and profit at high margins is not guaranteed, no matter what, you will always make the same amount of money per hour you spend. With silver grinding, as you purchase more machines, you can increase your yield and therefore money per hour, while with mining this is fixed.

If I buy a business IRL, it's not guaranteed to make money. There may be issues within the company I have to fix; there may be periods where our rivals control the market. My point is that, except for silver grinding, other ways of making money are variable. While silver grinding is always guaranteed.

So, to compare silver grinding to investing in a company, mining, or doing cargo contracts is simply not true. There is nothing at stake; there are no variable factors.

Solutions
Solution number 1: Maintenance of SF machines. I propose that certain SF machines have a durability, which would only start to tally up and accelerate in deterioration over extended use. Increased use or continued use would nerf the efficiency of production also. This would encourage players not to silver grind for extended periods of time, which would prevent the inequality between players who play for disgusting amounts of time silver grinding and players that enjoy themselves.

Solution number 2: Variable silver exchange rate. Make it so that the more silver a person grinds, the less value it has. Also, add randomized market fluctuations. This ensures less silver is being turned into money at a time and also adds a soft cap that prevents all the silver from being grinded all at once. OR, if a player does so, he still must wait however long the period is to exchange the rest of the silver.

Solution number 3: Fatigue. Perhaps the most radical, but make it so extended use of SF machines leads to a state of 'fatigue' where the player must wait X amount of time before using his machine. I.e., someone plays for 3 hours straight on SF machines and the server says you can't use SF for the next, say, 2–3 hours. This again reduces inequality between silver grinders and those who do less or do not.