It works out around £150 off-peak for two of us return and 2.5 hours each way by train and that doesn't take into account parking or transport to and from the station at this end.
Compared to £50-60's worth of fuel, door to car park and two hours travelling by car
I've been to various things over the years at the NEC and driven (or ridden) every time. Yes, you'll pay at least an orange picture of her Maj to park, but all I can say is that I've never had a problem with it. Easy to get to, and easy to get back out of.
I go several times a year, never had an issue, depending on the size of the event, the parking can be a fair walk - worse than that for a Yorkie will be the cost of a pie, a coffee or a beer. Take a flask, a packed lunch and a chiller box ?