ok but even if I scale it up with wider parameters to justify the potential discount on the new house.
a) It's still pretty flipping unbelievable - if you're now saying they spent 1million on rent over 11 years, and then saved £3million on their house - if said house was approximately £4million in 2008, went up to £7million c.2022 you're expecting us to believe the owners happily accepted a nearly 50% reduction less than a year later?
b) I can scale it up to help me "understand" but 99.99% of the population will never be able to "relate" to someone who can afford to spend that much on either rent AND saved sufficient extra money to put down on a £4million house while renting, or to even afford to buy a £4million house in the first place.
It also doesn't work if you scale down - as an example I've looked up houses that have just sold for the average house price (£285k) near me and found some that have sold prices in 2008.
None of them have magically reduced back down to that price or anywhere near- they sold for between roughly £130-140k then. So someone who bought in 2008 could sell for £145k profit today whereas someone who had been renting since then (or even "just" since 2012) would probably have spent well over £100k on rent and would have struggled to also save an extra £30k (for a 10% deposit) in the meantime.
So the fact it worked for your colleague is irrelevant as the vast amount of people will never make a saving worth 11 years of rent.
That's not to say that renting cannot sometimes work out better than buying - either logistically, financially, or just from a social/individual perspective - of course it can. But your specific example with the figures quoted, is completely unfeasible.