No not necessarily.
Most builders will advertise a "come on in and talk to us" price which will exclude a lot of things such as internal painting, light fittings, floor coverings, window treatments, fly or security screens, soakwells, landscaping, fencing, airconditioning, gas points, probably only half the powerpoints needed and a myriad of other things. Once they have you sitting down for a chat, the hard sell starts and you end up signing up for double where you started.
Our first build was a nightmare and a very steep learning curve but learn we did and from then on we were a lot smarter and played the game to our rules.
You will have to go through the process to get the experience and if you are not the type of person that enjoys a bit of argie bargie, you should appoint a project manager to do the leg work. It will save you money and agro in the long run.
These days we use an architect who who designs the house, draws the plans, liaise with the council, engineers, quantity surveyors etc. He draws up the very detailed specification and project manages the build. We happily pay him handsomely for his expertise, knowledge, experience and network of professionals and we get a great result at a reasonable price.
You have an exciting road ahead and you will make some blues and as long as you pay attention, seek advice from those in the know and learn, you will be all the better for it.
Good luck and enjoy the ride.
Cheers.
Chrisv.