Property developer Paul Blackburne has broken his own records for developing the most expensive apartments, with a penthouse selling for $19.3 million.

Mr Blackburne first broke the record in April last year when he sold the sub-penthouse at the OneSubiaco tower for $15.9 million, which eclipsed another developer’s record of $15.2 million in 2014.

In July last year he broke it again when he sold the penthouse in the same complex for $17 million.

But it was not enough for the mystery penthouse buyer, who also bought another sub-penthouse on the floor below, connecting the two abodes via an internal staircase.

Not only that but he has spent $3.7 million on neighbouring apartments for family members, taking his total expenditure to $23 million.

The penthouse now has 1450sqm of indoor and balcony space on the top levels of the 24-storey tower. This includes six bedrooms, two living areas, a music room, a private pool on the 350sqm balcony, a games room, private bar, a fully contained nanny suite and guest suite and a gym.

The buyer also gets 2400sqm of private residents’ amenities including a gym, sauna, pool, residents’ lounge, private dining and cocktail lounge and rooftop gardens and butler services.

Mr Blackburne would not reveal the name of the mystery buyer, except to say he is a returning expat. There are rumours that he is an executive from a global IT company who has been living in America for a long time. “We are excited to see so many returning expats jumping into the Perth apartment market for these high-end apartments,” Mr Blackburne, above, said.

“They can’t believe how cheap Perth is compared to where they have been and how high the quality is here compared to many other countries.

“We feel great about every sale whether it is $500,000 or $20 million. It’s a nice feeling to see people excited by their new home and a new phase in life.”