I was on the server recently and I was looking for a market like there is on Dark Trilogy. I think it would be a good idea for there to be a market on Agrarian +.
The reason the market wasn't added to AG is, its a challenge pack. Selling the basic items like cobble stone, lava and machines.... break the pack.
If I remember correctly, on AG3 that only yielded a "you do not have permissions to use this command" message. The Forestry Trading Station/Catalog would work wonders if somebody could post a tutorial on how to use it. Great way to trade materials for other materials.
Its right as they say, there is a /shop command, but no /market. The /shop is basicly a place where you can buy kits like kit Thermal expansion (TE) for real money