I have never heard the statement "government IT project comes in ahead of schedule and under budget"! :-)

That is appalling! It's a gravy train for some businesses. Not only is the developer to blame, but all the way up to the decision-makers at every level.
OK, there's the back-end, but, really, come on, what's the problem.

We had a client wanting a new site; we pitched and we lost out. The (now ex) client decided they wanted a "London-based developer."
I still have my contacts at the ex client and I am aware of the new site running in well over budget, and 18-months late. I know the original figures quoted by the other two London agencies and the winner of the contract was more than ten times our quote (they accidentally sent me the agency proposals).
Am I bitter, no, am I frustrated, yes, because we'd have done a much better job, too.

I have never heard the statement "government IT project comes in ahead of schedule and under budget"! :-)

That is soooo true, Mark_A

I think sometimes an issue is that the client does not freeze the specification and then permit the developers to work, rather they keep changing requirements on an ongoing basis which is a disaster for both costs and timelines.

In fairness, though, how often have you heard the statement “IT project comes in ahead of schedule and under budget” without modifier?

Back, way way back, in the day I had an HVAC plumbing company. Commercial job RFQs would come not just with blue prints but an inches thick spec book.

No one quoted the products specified by the architect if they actually wanted the job, instead one looked up the technical specs for each and quoted the cheapest possible equivalent (not in quality).

Then if one got the contract one sent in equivalence variance requests to the project engineer hoping to get them passed so as to make a profit instead of taking a loss.

Of course change orders can really pad a job! And for some reason bureaucrats and politicians are especially bad at (1) knowing what they want and (2) leaving well enough alone.
Note: if you haven't seen The Pentagon Wars [en.m.wikipedia.org] you really should. It's truth in fiction.

The critical point in too many contracts is merely getting in the door aka price it low to capture and then play the padding and exceptions game to make (1) it whole and (2) fleece the unsuspecting marks. Too much commercial and especially government contract work is one huge con that everyone involved goes along with.

Kiddies, do recall:

"I am from the government. I am here to help you."

(and never mention it is being done on the taxpayer's dime?))

No surprises here. If you want to look for a real website fail the US have several in that regard!