I chose Hilton Doha to have my quarantine in. Cost was just £211 (just over QAR1000). One of the hotels at the cheaper end. There were other hotels QAR 1300 and beyond. There is also a cheaper hostel type accommodation available geared for migrant workforce. The cost included transfer from airport to hotel, Covid test and end of quarantine certificate and three meals a day. Food was generally good and plentiful. It was dropped off outside my door.
The whole process seems quite efficient. I understand there were problems when the quarantine requirement first started but the authorities seem to be all joined up and have their act together.