The table below shows the cost of buying 10,000 ammunition using feso (portable ammo box) and vis (standard ammo box). Each portable ammo box contains 10,000 ammunition. Each standard ammo box varies in amount according to its type. For example, a Box of Pistol Bullets costs 32 vis from NPC (e.g. Emilia) and contains 150 bullets. This amounts to 0.2133 vis per bullet, or 2133 vis for 10k bullets.
The ammo charger is more expensive than the standard ammo box, and thus it will not considered. Ratio refers to the exchange rate of feso for vis, using the respective costs of ammo boxes.
|10k Pistol Bullets||12||2,133||1:102|
|10k Rifle Bullets||10||2,500||1:250|
|10k Cannon Shells||40||25,000||1:625|
|10k Crossbow Bolts||13||4,000||1:307|
In Orpesia server, a commonly quoted feso-to-vis ratio is 1:20. As such, the portable ammo boxes are not only more convenient (especially for Outrage Shot users), they also offer vastly better exchange rates. So, if you have spare feso to sell, it is probably better to spend them on ammo rather than sell them at the common 1:20 rate.
For other servers, compare your local rate with the above ratios.