I'm doing scrum and waterfall at the moment, customers are saying why is it costing so much? Managers are saying we're agile :-D what fun. We have design docs and requirements docs and epics and scrum masters and devops etc etc
“Hey, customer, looks like we burnt through half your budget and it doesn’t look like we’ll be able to complete the full spec on what remains…
I could ask you to increase the budget, but I think I have a better suggestion. You tell me which feature is most important to get in and well focus on that exclusively, and iterate on that until you're either happy with what you’ve got, or the budget runs out. Then lets take a decision on how to proceed from there if still needed”
You can choose to accept this or leave the customer to yell at and sue somebody else.