How about these spiffy looking trikes.

I don't think you will find a trike that weighs less than 50 lbs for less than a grand, and the ones on that link start at about 40 pounds. Weight is the big problem with a trike and unfortunately it is expensive to design it out. In case you were wondering, cheap two wheel road bikes weigh in the low twenty pound range. I would not want to regularly ride a bike that weighed thirty pounds, let alone forty, but if you ride less than twenty miles at a time it would be alright I guess. I also do not think very positively about trikes as commuter vehicles because of the low visibility to other traffic in terms of sitting position, but if you mounted a flag on it for extra visibility it would be adequate.