It's relatively cheap now, as the weather is getting oppressive and it's nearly Ramadan. I'd wait a few months (Oct/Nov onwards) but it does start to get more expensive and they may be limited to school holidays.

DXB has an over-supply of hotels (over 400 on tripadvisor) and it's a very competitive market. Check out the Premier Inn ... I'm told it's actually quite good ... or nearer the time on sites like lastminute, etc.

I usually benchmark DXB about the same as London but taxis are definitely cheaper. You can easily check the prices of attractions (e.g. aquarium, Burj, etc) online.