Allow me to weigh in here.
When you purchase a property on the market, whatever price you paid for that property is the market value. Why? Because if the seller could get more for the property, they would have.
Sounds good in theory, but not so in practice.
The last one I bought was under market value, no two ways about it. An out of town agent listed the place with old, crappy photos; failed to mention a bunch of the big selling points and amenities (I mean, ****, a new light rail stop 5 minutes away, going direct to the Sydney CBD was a few weeks from completion and it wasn't even mentioned!) etc and the first open conflicted with a few others that were quite similar so not many people showed up. I pounced.
I turned up at the first open with an unconditional offer, way below what I was happy to pay, and exchanged contracts a few hours later, taking it off the market a few days after it was listed. No one else had a chance.
I have absolutely no doubt that a higher offer would have come if it stayed on market, and it would have sold for plenty more if it made it to auction. Two of the area's most experience local agents found out (independently) that I was the bloke who bought it and both made an effort to congratulate me on the epic buy (it was in a piping hot market, too).
In this case, the vendor trusted the agents' opinion of its value, and took his guidance on the pricing which was not on the mark (whether the long drive to open it each weekend of the campaign which stuffed up his other opens had anything to do with his suggesting they take the offer, I'll leave to your judgement). The agent simply didn't know the suburb he was selling in.
A telltale sign was when I asked him about the rents. The tenants were paying $50/week less rent than market and he said they miiiight be ok with a $10 or $20 a week increase in a few months but it was a really good amount anyway for the area..