Big difference?
Yes and no.
I think you'll find one has quoted base salary, the other salary plus accommodation plus utility allowance. Fair enough, as you can take the accomm allow as cash. But misleading if you think you get $US12,000 per month (base) PLUS free accommodation!
The other figures seem accurate to me.
I'd suggest, in the strongest possible terms, a visit to Doha with your loved ones before you sign up to anything there!!