I think there's a case for it: Shergar was valued around £10 million in 1981 [0] which would have been equivalent to around £25 million in 2004, very close to the £26.5 million given for the Northern Bank robbery, and either way far ahead of the few million in today's money the article claims for the jewel heist.

[0] https://en.m.wikipedia.org/wiki/Shergar [1] https://www.in2013dollars.com/uk/inflation/1981?endYear=2004...