For a stock car or one with the exact bolt-ons the map was written for, an off-the-shelf map is usually enough. A custom tune is worth it once your parts don't match any map, you change fuel such as E85, or you've added a bigger turbo. Expect about $300 to $600 for a remote e-tune and $400 or more for a US dyno tune.
A remap is usually worth it on a turbocharged car that's out of warranty. A stage 1 remap costs about £200 to £400 and adds roughly 15 to 30 percent more power. It does affect insurance: you must declare it, premiums go up, and some insurers won't cover it, so check the quote before you book.
A stage 1 tune from an established tuner is usually safe for the engine on a healthy turbo car running the right fuel. The real risks are the clutch or transmission hitting its torque limit, faster wear on plugs and the turbo, and a warranty claim on the powertrain getting denied. Whether it's worth it depends mostly on your warranty and your gearbox.