- You can only have a maximum of 250 soldiers. This includes new recruits (not yet shown up) and soldiers in transit between bases.
- New soldiers cost $40,000, while their monthly salary is half that price, or $20,000. If you have the full 250 soldiers, they're costing you $5M/month.
- Sacking a soldier costs nothing. To do so, make sure the soldiers name is listed in the Sell/Sack screen. If it is not there, the soldier is probably loaded on a transport ship.
- It takes 72 hours (3 days) for new recruits to show up. Once at a base, it takes anywhere from 6 to 16 hours to transfer between bases, dependent entirely on distance. The minimum transfer time is guaranteed even if both of your bases are stacked right on top of each other. The cost to transfer soldiers is free, regardless if they are wearing armor.
- Statistics and names of new recruits are always randomly generated. See recruit statistics for more info, including the probability of getting the perfect soldier.
- A soldier's armor stays with them, including if they are transferred or fired. So it is LOST if you fire them when they have on armor. This is the only item that stays with a soldier. Armor can be seen/changed on the Soldier tab, or under Equip Craft.
- Only 100 items can be in transit (transferred between bases) in total at any given time. "Items" here means line items; one transfer of 200 Elerium counts as one line item. Soldiers (including new recruits) each count as one item. So, in the endgame, if you want to hire a ton of new recruits for high-psi screening at the beginning of a month, you can only have 100 on the way at a time. This leads to a theoretical max of 1,000 soldiers per month if you're doing high-volume screening (3 days for 100 soldiers; 30 days per month). Do routine inter-base transfers before hiring huge batches, because they will hog your transfer queue for 3 days.
Scientist cost $60K each in the first month to hire, plus $30K/month thereafter in salary. They also need Laboratories to work in and Living Quarters to live in. Assuming you have Scientists on-staff in blocks of 50, including Lab rental and Living Quarters rental, each Scientist costs $1.54M/50 per month. As a good approximation, a full Lab costs $50K per day to run. In other words, every research day costs about $1K. As most of the cost (97%) is per-Scientist salaries, it's a good approximation even if your Labs are far from fully utilised.
In addition, the up-front cost of hiring an extra 50 scientists, building the Lab and the Living Quarters, is $4.15 million. The first Lab-full is a little cheaper as 10 Scientists are already hired, the Lab is already built, and there are (some, but not enough) Living Quarters available. $2.8 million is a reasonable approximation for the up-front costs of the first full Lab. Generally more than 3 Labs is not considered useful. However even in the limiting case (infinite/maximum Labs), the up-front cost amounts to about $83K per Scientist - not a huge amount more than the $30K hiring each Scientist will cost you in the first month.
Labs Up-front (/Scientist) Daily (/Scientist) x1 $ 2.80M $ 56K $ 50K $1K x2 $ 6.95M $ 70K $100K $1K x3 $11.10M $ 74K $150K $1K .. xN $ 4.15MxN $ 83K $ 50KxN $1K
When you sack/remove any craft you also lose the craft weapons (and ammo) it is armed with, so it is usually prudent to remove the weapons before sacking the aircraft. This is most often an issue when upgrading your Interceptors, but also if you are getting rid of Firestorms or Lightnings that you no longer require.
Unfortunately you are unable to totally remove weapons - you have to switch (rearm) to another weapon type. Therefore, before you sack an aircraft, make sure you have 2 spare cheap weapons in that base. Switch to the cheap weapons that you would rather lose, and keep your Plasma Beams or whatever was on the aircraft. Also, if you sell the aircraft right away after you have begun to rearm, there will be little or no ammunition lost when it flies back home to the leasing company.
In theory the cheapest sacrificial weapon is the Stingray Launcher at $16K each. In practice an Avalanche Launcher at $17K each, is a much more useful thing to have laying around spare. So far from being 'free' to sack an aircraft (with the exception of the Skyranger), it is likely to cost you $16K-$34K to sack it, even if you are careful. If you are careless it could cost you half a million dollars cash, plus lost manufacturing time.
When you do decide to rid yourself an aircraft, the general practice is to arm the cheap weapons onto it and then sack it immediately. If, due to various circumstances, you had the throwaway weapons on the ship long enough for it to proceed to its rearming phase, don't forget to unload the ammo before sacking the ship so that you don't lose the ammunition as well. To empty the ammo, re-arm the same weapon onto the ship. This will empty its magazine. Obviously this is not a necessary step if you do not have any of that weapon's ammo in storage, but one you should take if you are still actively using them.
Seb76's UFOLoader has a fix for this problem, allowing you to remove all weaponry from an aircraft.
Soldiers, HWPs and Equipment
When you sack an aircraft the soldiers and equipment get off first, so you don't need to worry about removing them first. They will still be retained even if there is no more storage capacity left for them, but this will mean that you won't be able to purchase new gear until free space is once again available.