I occasionally wonder at what point does some stuff become too expensive? Like a stadium or new parliament building or something. The Olympic stadium cost over £700 million in the end - it's never going to turn a profit. Or if it could theoretically, it would only be so far in the future that it would've already needed to be replaced or was no longer fit for purpose. West Ham are only going to pay £250 million rent over the next century.
This bridge will be a benefit, but where's the money going to come in 30 years time when it needs replaced again (at a cost of £40 million ...)