Hi Ozb!
My mechanic had my car on Monday/Tues. It's the second time I've used that shop, the first time was fantastic. This week it went in for a service and some modifications. When booking the car last year I hadn't acquired one of the parts but had a quote from the supplier. The quote was $1980 so I asked the mechanic if they can match it or get the price close enough, I'll just let them order it since that was the norm for them.
It took 4 phone calls to actually make sure the part was going to be there on the date. Each time I had them confirm the price (Under $2000).
Parts fitted and when it came time to pay the shop was extremely busy and payment was rushed. It wasn't until I checked the invoice they had charged me RRP ($2050) + GST + Part Delivery putting the total at $2300 for the part alone.
From what I understand, the RRP includes GST so is the shop correct in adding GST again? I wasn't happy with a lot of the things the shop did but at least I know for the future to just supply my own parts.
Regardless of GST or not, the part should be under $2,000 as per the quote.
Delivery is fair at $45, but you shouldn't be paying more than RRP, especially if you were quoted under $2,000.
But really, they pay for GST first and then can claim the GST, so yes, you paid GST twice. Speak to the workshop, however how they calculate the price is up to them but should be no more than RRP or what they quoted you.
Personally, I always supply most parts to my mechanic (now I just service it myself), I don't get any nasty surprises and can ensure they are quality parts usually at a much lower price than what the workshop charges (who usually charge RRP, fair enough, it costs time (money) to order/hold parts). i.e. I can buy equivalent oil on sale at $30 for 5L, the workshop charges $60.