Chris:

Postcards in Australia would only be slightly cheaper than doing full on mail.

Names: About $200 per thousand plus setup - 5,000 min.
Postage: $500 per thousand (50cents per mail piece)

Min cost would be about $1,500 with postcards. (Haven't added the cost of the cards themselves.)

With costs like that you could market to the same areas loads of times just be doing flyers.

Michael Ross