Why Factory is by far the best map to scav on. (Advice for new players)

Time. While a woods or customs raid can have loading times of 4-8 minutes you usually load into Factory in 2-3 minutes. With the super close extracts that means you spend less than 10 minutes total on your scav runs while still making decent money. This also means that if you get lucky with your starting loadout you can extract right away. And since factory raids are so short it doesn't matter if you die. You only lose 5-10 minutes of your time and nothing else.
High frequency scav runs do add up. Scav runs can feel like a waste of time since you wanna play your PMC as much as possible to level up and do quests. But with factory runs taking less than 10 minutes you can easily push them in between your PMC raids. The starting loadout alone can be worth good money and if you make an extra 50-100k between each PMC raid it adds up quickly and allows you to invest more into your PMC.
Dead PMCs. Since Factory is extremely dangerous for PMCs you will find many bodies with leftovers or if you get lucky even good gearsets. Be like a vulture and look out for those juicy carcasses.
Free scav karma. Every extract as a scav gives you 0.01 Fence reputation. If you do 3 (succesful) scav raids per day on factory, which takes less than 30 minutes, that's 0.21 rep per week from extracting alone.