Learn English – Idiom for making up a false story as an excuse to get out of something

I wondered why no-one else had suggested the definitive answer, until I ran a Google search that showed it to be much more common here in Australia than anywhere else.

Winners are grinners.

or its long form

Winners are grinners and the losers can please themselves.

It is particularly apt that last night a high-profile (Australian) sportsman "won" a boxing match at the end of 10 rounds because his (South African) opponent believed the poster that said "12 Round Title Fight". Winners are grinners captures the spirit perfectly!

You might want a to use an actual, well-known economics term:

• R.O.I: "Return On Investment"

Or

• "Pays for itself"

You would then explain how the subject does this.

Or you might want

• "you can't make an omlette without breaking a few eggs"

suggesting that a price MUST be paid to get the intended benefit.

or

• "Killer app", short for "killer application"

which refers to the fact that the very first spreadsheet program for a personal computer allowed accountants|book keepers to justify the entire cost of purchasing an entire expensive PC system because it would divide their workload by a factor of 10 or more. If the computer ONLY ran a spreadsheet, it was worth the price to them. But a computer also does much, much more, like print layout for documents, art, e-Mail, etc..

You might want:

• "Get the ball rolling"

Which conjures the image of giving a boulder a tiny initial push to start it rolling down a hill, after which gravity will take over & keep it rolling.