I've not seen any dirty tricks. But I've only purchased in times when agents really needed the deal.
Read freakenomics. Agents have very little incentive to get an extra $5000 for the vendor for example. The commission on that little bit extra is negligible.
Which is why stats show realestate agents hold out a lot longer for a better price with their own houses compared with the houses they sell for others.
While I agree the agents do not get much for that $5,000 extra unless bonuses are used.
I worked in REA and had an offer of 520k and the vendor wouldn't accept it. Said they could sell it for easily for 550k anytime go ask them for more money. I advised him that i feel the buyers will walk away as shaking when signing the CoS. The property had been on the market for 8 months and the highest offer before was 490 or 495k (cant remember). The underbidder was 500k (20k less). Showed the vendor comparable sales and if the property was worth 550k and then comparable properties at 500k, which is where his property was worth. (advertised price went from 550k+ down to 520k+ to 500k+ and was at 490k+). Clearly if it was worth 550k and you were advertising at 490k there would be a queue of people lining up for the bargin of the centrury but there was no one coming through open houses or maybe 1 or 2 groups and anytime someone wanted to inspect we made private bookings.
Went back to the buyers they pulled the plug and went to the underbidder and they had put an offer in on another property leaving no buyers. Another 2 months went buy (place was vacant this whole time which again I said it was costing them money) and it sold for 510k from another agent (same agency).
So in this real life situation, the vendor paid an extra 2 months (total 8 months) because he wanted 550k but it doesn't matter what you want it is what the market is going to pay but also lost $10,000 on what was his best offer cause his pride.
I got nothing for having the best offer that wasn't accept except in my mind I could say 'I told you so' and that it cost him more than it costed me. The reason for accepting a lower price he had bought another place and needed the cash and yes I did go back to the 520k buyers saying the vendor is more accepting of offers but he had burnt my relationship with the buyers as they gave their best and didn't win (FHB) and still hadn't purchased, even though I never promised them anything or disclosed what the underbidder was (as their first offer was 500k and we negotiated slowly up to 520k) it was truly a good offer.
Would you risk $5,000 in a 1M purchase price? The vendor is the one who says yes or no not the REA. If you push for the extra $5,000 the buyer moves on and you are left with either the under bidder (could be 50k less) or no bidders which on a 1M cash at 3% p.a. could cost the vendor ~$600 pw. What if the vendor has already bought and need settlement or they will have a loans of 1.5M which interest without bridging of 5% would be ~$1,500 pw.
With the agent selling their own house they are the one who pays the consequences if it doesn't sell but if an agent says I think I can get another $5,000 and the vendor says do it and the buyer walks away who is accountable?