I bought a tiny block of land (300sqm) and needed a sophisticated architect to design a 4x3 building plan for me. Mark Anthony Design did a great job in maximising space without it being too cramped. We decided to go with a double storey design that was individually designed to suit to my needs and they listen to what you want. Stage 1 of the plans costs $2000, total cost of completed plans is around $8000. I think it's worth going to a proper architect for a good job. I am now awaiting council approval to build.
Approximate cost: $8000