The West Ham United co-owner David Sullivan is braced for the club to record a loss of up to £17m over their final season at Upton Park after a summer of heavy spending in the transfer market aimed at ensuring they start life at the Olympic Stadium in the Premier League.

The hierarchy sanctioned the addition of 12 players in the close season, as well as the arrival of Slaven Bilic as manager, at a combined cost of more than £40m. Their number includes the £10.7m forward Dimitri Payet, who joined from Marseille, as well as Angelo Ogbonna from Juventus and Pedro Obiang from Sampdoria. Nikica Jelavic and Michael Antonio have yet to represent the club but will have significant roles to play, while they also have four high-profile loanees to inflate the annual wage bill for the season to around £70m.

The dividends have been immediate, with Monday’s 2-0 victory over Newcastle United taking Bilic’s side to fifth in the table following up the eye-catching victories at Arsenal and Liverpool. Yet, while the necessity to remain in the division in readiness for the move to Stratford is obvious, the strengthening has taken West Ham to the limit of the Premier League’s in-house financial fair play regulations in terms of salaries. Indeed, if any additions are required in the mid-winter window then first-team personnel would have been to sold first to balance the books.

“I cannot remember a more exciting or successful window during our time at the club,” said Sullivan. “We brought in 12 new players at a cost of over £40m but that was only possible because [the other co-owner] David Gold and I made sure we dug deep to get the players we wanted. We thought it was important this season, with the move to the new stadium, that we bought players in every position to create the best squad and team that has been at the club since we arrived.

“As a result, we are now at the maximum wages we are allowed to pay under Premier League rules and, therefore, if we wanted to buy again in January we would no doubt have to sell someone before we would be allowed to make signings. It also means we expect the club to make a loss of between £10m and £17m this year, depending on where we finish in the Premier League and the number of games we have televised. This is indicative of just how seriously we took this window and the signings we wanted to make.”

West Ham’s only major sale of the summer was Stewart Downing to Middlesbrough for around £5.5m. Kevin Nolan, the captain at the start of the campaign, has been released while Jussi Jaaskelainen, Modibo Maïga, Guy Demel and Carlton Cole have departed on free transfers.