But whether the reality show will have an impact on local real estate, long after fans of the hit series have switched off their televisions, is as difficult to predict as the final prices.

Industry experts are divided on what effect the sale of the five Glasshouse properties in Prahran, which are secretly auctioned on Saturday,  will have on the inner-east property scene.

Some say if high figures are achieved, it will prove to developers there are buyers willing to fork out for larger apartments as an alternative to the glut of high-density towers squeezing on to the market.

Unofficial expectations of up to $2 million per three bedroom apartment have been thrown around for months, but on the eve of the auctions, Channel Nine won't speculate on numbers.

Sources believe the buyers with the deepest pockets are circling Max and Karstan's apartment.

Selling agents have been similarly careful in their briefing to the competing couples – there is nothing directly comparable in the area, in generous size and cachet factor, so anything could happen under the hammer.

The auctions are held under strict confidentially, with only serious prospective buyers who have registered with agents allowed to attend.

The results will be revealed on the season finale on Sunday, with contestants collecting the money paid above the reserves and the winning team receiving an extra $100,000. 

The Block started in Sydney's beachside Bondi 11 years ago, with renovations the following years in Manly and Vaucluse, before the production shifted to more-affordable Melbourne.

Dingle Partners' Anton Wongtrakun, who is selling Chris and Jenna's apartment, said if sales are lucrative, it will prove to developers there is a cashed-up market for more spacious, luxury apartments.

"If there is proven depth in the market it might encourage developers to consider more substantial properties," he said. "In inner-city urban areas, developers have been reluctant to scale up to this level."

Greville Pabst, CEO of property valuers and advisors WBP Property, has walked through the Glasshouse. Due to workmanship, furnishings and publicity, he expects the apartments to exceed market value and attract above $2 million.

But he does not expect big sale prices to be a dangling carrot for developers. "These types of properties offer limited profitability for developers, particularly given the high standard to which the properties in the current season are finished," he said.

"They may stimulate some level of added interest in the already popular location."

The man who built The Block empire, co-creator and executive producer Julian Cress, said he has sat during previous auctions with contestants who have won up to $700,000 and those whose apartments didn't sell.

Above making entertainment, Mr Cress takes seriously the business of building and selling prestige real estate.

"We are about creating boutique developments because that sits within our format," he said. "If this property was tackled by a developer, they would put in 50 apartments, but we put in six.

"Not only do we create properties of a level of comfort and luxury, but we also price them reasonably. When our contestants have made money it is because the reserve prices were realistic and gave the contestants a chance."

The season finale airs on Channel 9 on Sunday, October 12 at 6.30pm.