are you suggesting that Paris is [more] affordable for software engineers? Quick check shows that the prices in Paris are about E10K per square meter - basically SV prices while salaries as far as i know are significantly lower there.
I have only vague idea about Barcelona - quick check shows like it may be on the scale of E5K per square meter (it was $100K per 2-3 bdrm 20 years ago, so 3x-4x today seems reasonable) So you need to have like at least $60K salary - do they have that there?
Again, i'm not against high[er] density. I'm against it being suggested as the panacea for housing affordability crisis - as far as i see it looks like it may even worsen the crisis (at least for some less fortunate people - like relatively affordable low income communities being displaced by upscale new construction like we have happening everywhere in SV).
Please just show where higher density did help to alleviate the affordability crisis. I think even the massively empty apartments in all these massively constructed ghost towers in China aren't falling in prices.