Dude, the increment is in terms of percentage. So if your base is high, your increment will be higher. I'm assuming for B, the increment is 5%. That means your salary is around $4k now. You mentioned you're MX12, that would mean you've worked for at least 1 year, and this would be your 2nd year or 3rd year. Hypothetically speaking, if your starting salary is $3500, that would imply an increment of $700+ in 2 - 3 years, which isn't too shabby isn't it?

It's not like you're on any programme nor are you a scholar. This is the fate of farmers in the public service. If you do slog it past the initial 10 years, you will enjoy better salary, better bonus, better increments, and have good job stability.