Hi
I would think the prices would be dependent on how far the land is from Builders and sub-contractors, how much work is available in the area for them, and transport costs.
Generally, if the area is pretty well serviced by suppliers and tradies, a Builder would be better value and the plan would be more flexible. You also have whatever State Regulatory Board for protection if things go awry, but they may well be as week as water. If you go this way make sure everything is in writing including variations, specifications and inclusions in the price. If you are unsure on anything, get it clarified in writing.
Kit Homes can be economical if you are prepared to do a lot of work yourselves, however if you need to take time off from being productive it will cost you more, and prefabs can be good because most of the material supply and labour is locally sourced by the manufacturer and the transport, elect, plumbing and drainage connections are the main things done on site.
Most subcontractors and suppliers charge an owner builder more than a builder who gives them more regular work, so everything you get done costs more. This can end up costing more than a builders total price, take longer, and end in an inferior product but at least you have a sense of achievement.
I have seen cases where people from outside well populated areas receive a quote from a builder who pumps the price up because he doesn't want the job, but if he does get it he makes a tidy (rip-off) profit.
Then when the person decides to go owner builder, it comes in cheaper, although they take 6 months off work to build it, and then write another book on "How To Be An Owner Builder and save Thousands" and make $23.50 off the sale of three books, but it cost $15 000 in editing and printing.
In Brisbane a few years back I was working for a Builder that built standard houses and added around 25% for overheads and margin. We also sold the same plans as Kit Homes and added 35% to 40% to the cost of the main structure and plaster. That was effectively a bonus for doing a lot less work than building.
Prefabs have limitations in designs and sizes and material choices unless there is a bit of on-site construction adding the pieces together, but cost wise work out pretty well as there is limited trade work on site. These can also be quicker as the factory production style has less delays for weather and material supply.
Depending on the Local Authorities approval, relocated homes can be good value especially if more modern designs with the open plan you want are available.
Buy the house, move it on site and connect the services, and quite often all you need to do for the Council is repaint it. Banks don't particularly like to finance these but it can be done with a bit of research.
I don't think there is a simple answer to what you want, but there are options with a wide range of possibilities.
Good luck with your endeavor.
Cheers
Ian
