RBS et al didn't need to invest that much in tech ....
...... as they used to have a large number of highly skilled techs that maintained existing systems while upgrading others for newer functions. They had a history with all of the systems and knew what would work and what wouldn't even before testing had started.
This would have allowed them to replace and upgrade over time with minimal disruption.
Then they decided, in order to save some money on the balance sheet and give some more clueless middle management extra bonuses, to offshore all of it to techs with no experience of the systems and their quirks who were taught by people who did not have that level of experience either.
So now we have a majority state owned bank losing more money through compensation than it saves from off shoring having to spend even more money to replace systems their 8000 mile away techs are unable to repair.
And still no one senior has been sacked for the complete shambles.