I agree with you. Outing a limit of say 18 - 20K on salary is not fair. I can very easily provide my family (wife and a kid) a very decent living in 15 - 16K. Its up to me if I want to save something or not !!!
And if they are really raising this limit by almost 60% (from 4.5K - 7K), then they should also instruct the employers to raise the basic salaries by 60% of the employees who have basic salaries less than 7K !!!

And on the other hand, one thing they should really be focusing on is to control the hikes in prices of living, specially accommodation !!!

A rich govt like that of Qatar can very easily do projects of housing and provide people with affordable and good accommodations, but the fact is, they really don't cars for expats, as its mostly the expats being affected by high rents!!!