Partially famous for being the remotest big city in the world, Perth is not the sort of place that you end up in by accident. A mining boom not far away has helped transform this into a big and rich city that rivals Sydney and Melbourne in some ways, but Perth is also somewhat famous for being expensive.
Hotels in Perth can actually be good value, and hostels are also fairly reasonable by Australian and international standards. Quality is good as long as you avoid the absolute cheapest places. Attraction prices are similar to those in Europe or the United States, so you shouldn’t have to skip the things you’ve traveled all this way to see.
Food and drinks, however, can be quite expensive in Perth, as they tend to be all over Australia. Even fast food meals and casual restaurants feel pricey compared to most of the rest of the world, so backpackers self-catering at the hostel kitchen might be necessary for those on the lowest budgets.