Newty has the numbers right, coz 8100 is assuming 70hrs. The bond was 3 years when I was in Doha 5 weeks ago, but you only pay half of it (25k) during 18 month. (it is a little confusing) you pay 1388usd per month the first 18 months. Then no more salary deduction. And you get all your money back after 36 months.
I think that is how it works