I am not sure why everything has to be compared in terms of all or nothing.
In this case specifically, they knew that they're playing a loosing game since Apple and Google are ultimately the gatekeepers of the gadgets doing the actual tracing.
Thinking that somehow the UK has the individual power to go ahead and reasonably do it's own thing is nothing but arrogant.
ETA: sources in grandchild comment.
I am trusting Kenny Paterson at ETH Zurich on the cost of the Swiss app, since he was involved in developing it: https://twitter.com/kennyog/status/1273612397861842950?s=20
ETA: NYT article also mentions a "secretive procurement process" for the UK app, which sounds a bit worrying.
Sadly this is unsurprising and par for the course for the UK government these days.
Not particularly secretive, just a bit bureaucratic.
Does the G-Cloud procurement website have any details on where the 108M was spent?
[1] Random website I found when googling, grain of salt etc: https://bylinetimes.com/2020/05/08/nhsx-contract-tracing-app...
Because of protests and massive intervention of experts and digital citizens rights group like the CCC.
Luckily, the government listened in this case. I am somewhat amazed how well different sectors of society can suddenly work together when the situation is serious.
It's the same strategy non-democratic regimes use ( Trump, China, Russia)