I think that's country specific. For example, for Denmark its £4.70 for 5GB [1]. Thats probably cheaper than buying a local sim and worth it for the convenience especially as I tend to use far less than that and only need 1GB as I'll just go for a few days. Then I may as well pay for the £1.10, 1GB option.

1. https://esimdb.com/denmark/bnesim