Welcome to the Bunnings Workshop community @PattyH01. It's fabulous to have you join us and many thanks for your question.
Natural light is always of great benefit inside a home. It can reduce electricity costs, provide the illusion of space and increase property value.
The installation cost for skylights can vary greatly and is determined by several factors. The type of roof (tile/metal roof), roof pitch and style preference will come into play. If any electrical cabling needs to be relocated that will be a cost to consider as well. There also needs to be space for any additional framing required to support the skylight or modifications to the existing structure.
My suggestion would be for you to start by getting several quotes to compare pricing.
Let me mention the ever-helpful @redracer01 to see if he has some opinions on skylights.
Please let me know if you need further information or had any questions.