Magdalena, if you can get $5500-$6000/month then the offer is worth it.
This is provided your employer gives you an adequate housing allowance. Check the forum for all the housing cost threads. It's not cheap. You have to take into account medical insurance, transportation, vacation time, annual airfare and education costs if you have kids.

Doha's fashion design scene is not exactly Paris or Milan haute couture so be careful who you're in business with.