Your price of $65-100k on the build is incorrect. What about footings, retaining walls, AC, floorings, storm water, paths, drive, etc.First, always remember a rule - when you are spending hundreds of thousands, it is painful when you have to sell for less than you paid, and it always feels nice when you make some money.
As I said many times, capital gain is only achievable when you buy land that is in short supply. And this is NOT land in new housing estates, which multiply in Adelaide at the rate of bacteria.
The only land in short supply is land on waterfront or land where waterviews can never be built out. Even in theory. Everything else is a waste of money, especially if you are forced to sell during property downturn. Waterfront is like a buying insurance for your money.
As to house and land packages. The term is deceptive on its own. The builder buys land for you, and they do it for the profit. Money wasted. You would have negotiated yourself the price of land with the owner that is much more competitive.
Because the builder sells you a "package" (means you do not want to save money on buying the land yourself) - this is the signal for a builder to overcharge you on building.
Two listings for the same block of land:
1.Land only (range $220-$240K)
2.House and land package:
Lets look at the first case.
Does not take a rocket scientist to work out lowest acceptable offer when agent specifies price range. Lower boundary is set to attract lower offers so agent can tell the other purchasers "We have had plenty of $220K offers, all of them were rejected". The money owner wants - it is right in the middle. So you can get the land for $230K - guaranteed. The land has an approved plans for three bedder. Single storey three bedder if built by say Rivergum homes is going to cost you anywhere from $65K to $100K depending on inclusions. In other words, the whole "package" is going to cost you anywhere between $295K and $330K.
If you take the second option (Weeks and Macklin "house and land package") it is going to cost you some $100K more than the same thing "unpackaged".
How Weeks and Macklin have set their price? Extremely simple. In this place you would never be able to rent a house on a waterfront for less than $400 a week. $386 a week mortgage repayment is whole $14 a week lower than the lowest rent.
The same old selling line - why rent if you can own brand new home for less.
Unfortunately it seems that there are too many wealthy people around who do not mind to pay $100K extra just for not wanting making an offer on land themselves and hiring a conveyancer. $100K is not bad for 10 minute job.