Not entirely sure what you mean by the money drying up.
Anyway, my point was, that the biggest lumps of money are invoiced towards the back end of a project. So saying that it's nowhere near half way cause only £100m has been 'spent' is a bit of a false equivalence. The physical build isn't halfway, but the stadium project is over half way.
Also, may be worth saying, that as much of the project is being manufactured offsite, much more of the stadium has been manufactured than what you see onside. Also, the steelwork will be invoiced as it arrives. Depending on the contract, that invoice will be based upon arrival the site, or the facility. So probably not correct to say that 'only £100m has been spent anyway, certainly when considering not insubstantial design costs and the £100m site prep costs.
Would be good to have a look at the construction program though.