It seems a number of hotels have pulled out, restricted drastically the capacity they offer to the scheme, or beefed up their pricing. Maybe Doha is getting popular enough for hotels not to need this form of support.

The "standard" level still go for £20 a night for one night stays, There are perfectly OK hotels in this group, though some of the nicer, more recognised hotels are out of the listing or appear only rarely. The Holiday Inn still heads QR's visual presentation of the standard group, but is no longer available: neither is Sheraton Four Points. Quite weirdly longer stays attract higher daily rates, so that a (maximum) 4-night stay is somewhere over £30 a night.
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Top hotels start at £70 a night but go up alarmingly for, say, Mandarin Oriental at £280 per night - but at least these hotel include breakfast in their rates...

Clearly this last group are not always particularly good value, especially if you have a magic card that gets you breakfast anyway. But if you're looking for a comfortable base for a one-night stay - you can still get it for a modest outlay.