Comment by kristianc
Part of this is a product of the UK's political culture where expenses for stuff like this are ruthlessly scrutinised from within and without.
The idea of the site hosting such an important document running independently on WordPress, being maintained by a single external developer and a tiny in-house team would seem really strange to many other countries.
Everyone is so terrified of headlines like "OBR spends £2m upgrading website" that you get stuff like this.
It's not an easy call. Sometimes, one or two dedicated and competent people can vastly outperform large and bureaucratic consulting firms, for a fraction of the price. And sometimes, somebody's cousin "who knows that internet stuff" is trousering inflated rates at the taxpayer's expense, while credentialed and competent professionals are shut out from old boys' networks. One rule does not fit all.