Why have I heard such a big range of prices for bathrooms from other people?

For several reasons. The overall price for your project is made up of many components, lots of which are individual to you and your design and preferences. Others may have different budgets or tastes or place a higher value on particular items.

The largest components by far are the materials and labour, materials being the items within your bathroom such as toilet, vanity, shower, tiles and windows, and labour including the builder and carpentry, electrical, plumbing and waterproofing. For which it is self-evident that you do not always want the cheapest tradesperson.

In addition, many reputable renovators have good supplier and trade relationships and can get high quality products and services for their clients. Others may reduce prices by using less favourable suppliers, discontinued items or a lesser quality of materials.

On costs that add a small amount (a few hundred dollars) to your project but are invaluable include qualifications, licences and registrations.
In general, if there is a small difference in price between your quote and that of others, ask us to go through it and compare ‘apples for apples’ so that you are well informed before making a decision. If, however, you are presented with a surprisingly low proposal for any building works, approach with caution and do your research.