Looking for AU RRP of some old sets

I'm new to this forum, so please excuse me if my questions has been answered somewhere else.

I'm compiling a spreadsheet of all of the sets I've bought in the last few years, so I can compare how much I spent on them with the Australian RRP to figure out how much I've saved/overspent, and if I decide to sell any of my collection, I can keep track of the profit/loss I made on each set. I only found out about this site recently, so I realise that I could do a similar thing with the brickfolio, although I'm having issues with the bulk import from Brickset, as it is importing the prices as USD, not AUD (I'm not sure if this is just a display issue or an actual bug). In any case, I have reservations about storing data on other websites, primarily in case they stop working, I lose all of my data.

I've managed to find the RRP of almost all of the sets I own from various sources (the Price Guide on here, The lego shop@home page, and Brickset's prices tab). Firstly, I've noticed that for a lot of the more recent sets, in the last couple of years, the Prices Guide on brickpicker is missing the AUD RRP. I sent a message to the Admin about this, but haven't heard anything from them, so I was curious to know how this data is updated? Also, I have a few older Technic sets which I could not find the RRP from any of these sources, and was wondering if anyone on this forum could help me with finding them?

The sets that I would like to find the AUD RRP for are:

• 8063 - Tractor with Trailer - Released 2009 - USD RRP $99.99
• 8274 - Combine Harvester - Released 2007 - USD RRP $69.99
• 8284 - Dune Buggy/Tractor - Released 2006 - USD RRP $59.99

I may eventually be looking at selling some of my collection, and was wondering if I end up making a profit, what the tax implications are? Does anyone have any experience with this. Also, where is the best place to sell sets on, Bricklink, Ebay, Gumtree, etc, and what kind of postage costs am I looking at paying?