Cheaper than a $0.39 hamburger? Where?

What currency are you using? In USD, the cheapest item on the menu that I can find (apple slices) goes for $0.57. A big mac combo goes for around $10, while a subway footlong goes for about $7.

$10 is also a pretty wrong number for "hamburger". Looking at this ordering form, I see $2.49 for a mcdouble and only $1.39 for a basic hamburger. And the mcchicken is $1.19

(Though wow, mcdouble was half that 2-3 years ago. Big mac hasn't really changed.)

I do recall an article from a few years ago about how the basic McD burger was arguably the most bang-for-your-buck in terms of calories per cent, and I agree it's hard to beat (though not impossible, e.g. the costco hotdog combo costs a measly $1.50 and packs ~3-4 times more calories)

But yeah, a lot of the McD classics and new offerings that one might purchase for a "normal" meal are actually quite expensive nowadays. On a side note (pun intended), I suspect that there are some pricing structure shenanigans going on, because fries are clearly marked up way more than burgers.