I'd just like to point out that OP is either lying or has been scammed.
Starbucks have consistent pricing and the most expensive sandwich in the UK is £5.10, technically 5.25 for a plant based breakfast item, see here for full menu prices.
But people like getting angry at cost of living issues right now (understandably) so this will get hundreds of upvotes despite being a lie.
Still a stupid price for a crap sandwich. As I said in another reply, come to France and you will get the same thing for half the price. However, it will be nice (can you beat french bread? I think not)
Well that depends on the baguette. A cheap baguette moulée I agree. A nice tradition will be take around 72 hours to mature to the point it can successfully be used for violence.
I may live in France, but I am English too. A simple white cottage loaf is great, that is indisputable. However the availability is laughable.
When I lived in Portsmouth, there were 2 bakeries on the whole island. 2!! in my little town here we have 4 artisan bakers, plus 3 supermarkets that all sell really good bread. Just round the corner from my house there is a farm that sells bread (made completely in house) every Friday afternoon and people take the afternoon off work and drive 2 hours to buy it.
French bread wins hands down.
However I agree with you on one thing: I love bread!
Maybe more than in the UK, but here in a supermarket that would be 0.20€ of ham, 0.10€ of chese and 0.30€ of bread. Considering the volume starbucks has, I don't think it's unreasonable they would pay half of what you pay in a supermarket.
Of course these numbers I'm all taking our of my ass, but I think they are a close estimate. There's a reason if Starbucks is so profitable