I've bought tickets via Songkick on a number of occasions. The app has transformed my ability to buy tickets (previously I always found out too late that tickets were on sale).
From comparisons made at the point of sale tickets appear to be no more expensive than if bought from the venue directly.
And for a recent concert, when I realised on the day of a concert that I couldn't locate the tickets, replacements were made available and were ready for collection on the door that evening - impressively swift service.
Highly recommended. My only reservation about posting here: the more people use Songkick the less chance I'll have of getting tickets..!