High than market prices from my experience are vendors with an unrealistic opinion of how much their place is worth. Spoken with a few agents that openly admitted the place was $100-200k above what they expected it to sell for but the owner was insistent on it being listed at that price. Naturally over 1-2 months the price comes down or they end up changing agents and eventually it sells for what you thought it would initially.
The suspect practices I see from agents in South West Sydney is actually the opposite. They list anything going to auction with a price guide $150-200k below what it will sell for. The aim of this is to get as many ppl as possible through the doors and at the auction. Looks like there is huge demand when actually only 2-3 out of the 10 bidders actually have the coin to buy it. A full yard of bidders makes those with the money bid more because they get fomo.
