I would have to say, having got to know the potential design quite well having modelled it, it is clear to me that this is not a stadium design design even slightly comparable to the emirates, ethihad, the spurs stadium etc, which are all modular, repeating prefab construction that makes it quick and affordable to build. The very asymmetrical nature of both the footprint of the stadium site, and the asymmetrical nature of the stands and the extremely complex roof, constructed with out a single repeating truss or beam in the entire design, I would guess that this will be closer to the billion than 500 million. Nothing in this design is repeated. Every butress, roof truss, stand, every component is one off and unique. Stadiums like arsenal's city's and now spurs all look the same because that is the most efficient design in terms of cost and build time. They're cookie cutting stadiums because those designs are easier to build. They don't copy each other's stadiums because they are interesting archetecture worthy of a pastiche. And yes, one could argue that each stadium has a unique element, spurs will have their 'unique' and 'original' Kop end design feature to distinguish their stadium from the modern blueprint for stadiums, as an example, but the stadium itself is just an imitation of the modern standard design. For example, consider arsenal's stadium, and compare it to the benfica stadium. The are literally twins. Not to copy each other, but because that design is the tesco value brand of stadiums. They are perfectly good, efficient designs. And chelsea would very likely build like that too if space permitted. But whilst very cost effective, they are very dull.
Chelsea's stadium, because of the complexities of the site restrictions, and the art loving nature of the owner (abramovic is a serious art collector, and often commissions very exciting archetural projects) too will have a truly bespoke stadium. Custom made and really the only truly unique new build stadium in England so far. The design is not cost effective. In fact, when the club considered just extending the Mathew Harding stand, just a simple extension was estimated to cost £23,000 per additional seat. So, with all this in mind, i can not see how chelsea could possibly demolish, then build the bridge for 500million, when spurs will spend that amount to build on an already cleared brown field site, and construct a comparatively simple, common design.
No chance. Arsenal's and Spurs were/ are £400-500 mil, the Olympic Stadium £700 mil and Wembley £800 mil. Unless Abramovich intends to plate it in gold, It aint going to cost more than Wembley.