The Block‘s bizarre octagonal shape creates a puzzle for property valuers, buyers and real estate agents.

With nothing else like it on the market in Melbourne, determining how much the five luxury apartments will sell for is no straight-forward task.

Even the teams are unlikely to be told their reserves until the eleventh hour.

The winner of The Block is determined not by the team that achieves the highest auction price, but by the greatest margin over reserve.

Occasionally, Block properties have wildly varying reserves, influenced by their different pros and cons.

Buyers advocate Karin Mackay has bid for several Block properties in the past, including the Triple Threat townhouses in upmarket Darling Street, South Yarra, last season.

Ms Mackay predicts the sixth-floor penthouse of the former Hotel Saville in South Yarra – renovated by young Townsville couple Dean and Shay – will sell for about $1.85 million.

“I might have gone to $2 million, if I was bidding,” she said.

“Apartment number one, with the graffiti bath (belonging to Kingi and Caro), I loved the kitchen and would have paid around $1.65 million. I would have paid $1.65 million to $1.85 million for everything else in between.”

Ms Mackay said the location didn’t meet the criteria for her prospective owner-occupiers. She advised clients against throwing their hands up at the Blocktagon auctions.

“Mainly it is the noise and the fumes, and concern if the (neighbouring) petrol station ever caught on fire,” she said.

Melbourne Deluxe real estate boss Paul Pfeiffer said he “can’t see them hitting $2 million”.

Mr Pfeiffer said he expects most to fetch between $1.7 million to $1.9 million.

“I think they will struggle, because I think Darling Street was a better proposition, although Darling Street didn’t have a lift and so that closed out a section of the market,” he said.

“These are unusual properties and in a busy location.”

Mr Pfeiffer said The Block properties have a sprinkling of magic dust that encourages buyers to pay a premium.

“Definitely that was the case last series – if you put those back into the market now you’d likely lose money. It has the glamour of the television show, but market sentiment isn’t that great at the moment.”

With the finale screening on Wednesday night, the results of last Saturday’s closed door auctions, in which only buyers and their representatives were allowed to attend, are confidential.

The properties have gone to auction just as the Melbourne market comes off the boil.

And a dropping clearance rate can contribute to poorer results for Block contestants, according to finder.com.au

Melbourne’s clearance rates are sliding, clocking in at 66 per cent on Saturday, down from 70 per cent the weekend before.

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Finder crunched the numbers and found that for all seasons in which at least one property passed in, sold for market value or transacted for as little as 10,000 over reserve – including at last year’s Glasshouse series in Prahran – the average monthly suburb auction clearance rate was around 53 per cent.

The Block auction finale is on Channel Nine on Wednesday at 7.30pm.