Meaning of しまえ in Japanese

一昔前だったら、駅や、レストランや、病院の待合室でタバコに火をつけるのをためらう人はいなかっただろう。
At one time, people would not have hesitated to light up a cigarette in stations, restaurants, or hospital waiting rooms.

こつさえ覚えれば、朝飯前ですよ。
It's a snap once you get the hang of it.

「騙された」と言ってしまえばそれまでですが、「うまい話」に乗った当人であることは間違いありません。
If you say "I was tricked," well that's certainly so but there's no mistaking that you were the one who signed up on a "sweet deal".