After 35 years working for owner builders and building firms yes you definately save lots of money by getting rid of the builder
The only reason you exceed the budget is because you have the final say as an owner builder and inevitably you make things a bit bigger and you change items as you go...try doing that with a builder and see what extra they charge

I've seen major firms charge owners $5000+ for little extras that would only cost a few hundred and then I've seen owners agree to a price but when the jobs done they argue about how much it cost

Shows like the block and my Renovation give the normal person with no experience in building a false view that only a few people are involved in the process you don't see the other 30 people behind the scene

My husband and I are nearly at the end of a major owner build - before this the biggest thing we had built was a farm shed... Based on BMT's current building cost calculator we will have saved over 50% of the replacement cost of our home by owner building - it has been a hard slog but worth it in the end. Our valuer has indicated that at completion our mortgage will be around 30% of our properties value, which means we will have built in a LOT of equity. It's not for everyone but if you can - I say go for it!

My lessons learnt so far:

Go the extra mile in ensuring your plans are detailed/you have incorporated EVERYTHING you want in your new house before starting - major budget blowouts are inevitable if you keep changing things mid-stride! Have a plan and a budget and work to it:) Have a bill of materials and specifications that includes everything - even down to the brands, there is a major cost difference in a garden variety Bunning's vanity vs. a bespoke custom floating one - and unless you specify exactly what you require you will not get what you want and your budget will never be accurate (and your cost overruns will be scary!).

Decide what level you want to be involved at: do you have plans to be hands on - building everything you can, learning all the trades like framing/plastering/tiling etc. or are you envisioning a owner-managing role where you are engaging trades to complete the work for you; this will dramatically alter the cost and the time the project will take. Will you be able to be present on site when trades are there to manage them? One of the major things a builder does is crisis control and problem solving!!

Bespoke architect or kit or somewhere in between?? Another thing that will bear greatly on cost and project staging. For first time owner builders I would recommend a kit home - most of the inclusions are standard, you can modify many of the designs and the deliveries are staged so you don't have an influx of materials all at once. Most of the kit home providers are great with their after sales support and advice when you need it - they wan't to see you succeed as their business relies on successful customers!

Ensure your finance is concrete and you are able to draw down funds as you need them - this is a major stumbling block when it comes to owner building as most financial institutions will not loan to owner builders. There is nothing more frustrating than getting halfway through a build only to find out that due to prevailing economic conditions your current lending provider will not loan you any more money and you have actually devalued your property by partially erecting a home (oh, yes sadly- I'm speaking from experience...). Build in contingency funds to any estimate of costs - you will sleep better at night. Be aware that even if you do obtain construction finance that most banks will pay these retrospectively - you have to spend the money before they will draw it down off your loan - that means having enough money to fund a stage in full ( i.e. brickwork, plumbing, electrical) before drawing down loan funds - and you can be guaranteed they will want to send round the valuer to ensure that the work has been carried out!

Have written quotations and lists of inclusions/bill of materials when negotiating with tradesman and contractors - many are happy to work with you but a lot will take advantage of your naivety... Don't be left out on a limb after getting to the end of the job only to have your contractor demand large blowout payments - this is readily avoided by having everything in writing and will ensure your contractor keeps you informed of any expected costs overruns.

Do not underestimate the impact an owner build will have on your life... You will be eating, living, breathing and dreaming it for as long as it takes (and yes there will be nightmares!). Be honest with yourself about how much time and commitment you are willing to sacrifice to make the cost savings worthwhile - if you are the kind of person who begrudges any intrusion into your personal time, can't go a week without a social occasion and can't handle working long hours and getting your hands dirty...maybe owner building isn't for you...

Enjoy the journey! My husband and I have tackled every job we have been capable of - we have put up the framing, put on the roof, done the guttering, installed the insulation and windows and we are plastering the inside and painting as I speak. It has been good to learn new skills and exceptionally rewarding to see it all come together - sure if I had my time over again I would have done a few things differently but we don't regret the decision to take charge of our future and build our own home just the way we want it. Anything is possible if you give it a try!!