I look at it a bit different.
You spend big bucks for flights, green fees, lodging, food, swag, pub time, etc. But heaven forbid you spend a little extra for a car rental!
If you want to go to an area or club regularly and play in some events, it is easy and saves the cost of a car and potential damage to a rental car. The insurance can also increase the cost significantly.
As a former long time commuter to NYC living on the Northeast Corridor line NJ -USA I am used to hopping on a train, and you can even grab a quick nap.
With essentially zero tolerance on drinking in UK and Ireland you can't really drive anyway after hitting the bar or pub.
My son and I took the train roundtrip to Edinburgh from North Berwick last Tuesday afternoon and the off peak fare was a little over 7 GBP.