Question: I'm currently attending a basic course on real-time embedded systems. Recently, we have been talking about embedded systems memory architecture. When doing some extra studying on memory maps, I came across the memory map for the ATmega328P microcontroller. As can be seen from the image, the flash is divided into a boot section and an application section.

[![enter image description here](https://i.stack.imgur.com/NWBNO.png)](https://i.stack.imgur.com/NWBNO.png)

Why is the boot section not starting from address 0? As I've understood it, the microcontroller application won't run without a bootloader. So why doesn't the bootloader occupy the lower addresses if everything else relies on it?

Answer: 
Well, even your first assumption is wrong.

Audio DACs are these days are not even constructed from R-2R resistances. Even a 1-bit delta sigma modulator will likely have better specs on audio bandwidth than a bunch of resistors. The problems of analog domain are handled by processing in digital domain.

Usualy the price of a product is just dependent on how much money and effort has been made designing it, so careful design generally makes a more expensive product. Careful design includes selecting and evaluating reliable quality components, designing the schematic and good PCB layout, maybe even using a more expensive 4 layer PCB, and maybe the look, feel and materials of the case to justify the high price. It may include more software features than other products, so it takes longer and more money to develop features that may even be rarely used.

But remember that selling a good looking product at a high prive does not mean it's Hi-Fi, it's the specs.

And sometimes, these devices go just overboard with the specs, maybe forced by the marketing department. For example, your ears hear up to 20 kHz, and likely the material you play is recorded to 20 kHz, so why would you need a DAC, amplifier and speakers that can play up to 40 kHz unless you are a bat.
Good comprehensive posts, so just a couple of cents in addition:

For audio reproduction, perhaps the key property of the DAC is its nonlinearity, or Integral Nonlinearity (INL).

R2R DACs don't offer advantages here, so are being successively abandoned in favor of cheaper and more flexible Delta Sigma DACs. Digital compensation for INL also favors Delta Sigma DACs as they implicitly come with beefier DSP units integrated/attached.