with prices a record 19 times....

Just come across a sentence in the newspaper like this: -

HK has hte least affordable housing of 87 major global cities, with prices a record 19 times avearge pre-tax household income, a new survey said.

What baffles me is the mid sentence: -

'with prices a record 19 times average pre-tax household income'

I suppose some words were omitted. If I understand correctly, the 'long version' of the sentence should look like this:

'with prices being a record of 19 times the average pre-tax household home'

Frankly, I'm so bewildered by this sentence. I really don't understand why this sentence (I'd call it a prepositional phrase because it begins with a preposition and has no 'verb') is constructed like this.

Could you elucidate the grammar and/or sytactic rules behind this and illustrate your points with some sample sentences?

Thanks!