I already own this, but for anyone wondering, it's not a bad price for the unit, considering it goes for around $250-$260 on most other stores. However, I got mine through Shenzhenaudio for $221, and they have free fast shipping worldwide (I live in the US and got it within 8 days of ordering), so the price here really isn't anything special either unfortunately. Shenzhenaudio was even nice enough to include a compatible torx driver for me outside the box.
They also sell the new 05bl Pro bluetooth module, which is an updated version of the old 05bl that was released originally for the XD-05 (though it was also compatible with the XD-05 Plus), for a lower cost than I've seen on most other sites ($58). There's a couple listings on eBay that are cheaper by a few dollars if you don't mind waiting weeks to get it. The Pro model is updated to support USB-C as well as aptX HD/LL and LDAC. The release of the 05bl Pro is actually what finally pushed me to buy the XD-05 Plus, as I had been trying to decide between it and the Fiio Q5s for some time, and one of the main things attracting me to the Q5s was its LDAC support. You can see what the module (05bl and 05bl Pro look nearly identical) looks like when attached in the last product picture above.
I'll also include this bit in here so more people see it, but I've left a similar comment as a reply on a couple other posts below. As some people have noted, a standard USB-C to USB-C cable will not work as intended with the XD-05 Plus. I don't believe this is out of any malicious intent to sell proprietary cables however, especially considering I can't find their cable on sale separately anywhere. I believe this has something to do with how USB type C works, and an attempt to utilize a more efficient connection between the phone and DAC.
On older DACs that use USB Micro B ports, you're usually required to use an OTG adapter on the phone, which forces the phone to act as a USB host. This means that, much like how your PC supplies the power for USB peripherals attached to it, your phone is forced to send power to the DAC. That is not to say the DAC is fully powered by the phone as it utilizes its own battery, but a certain level of power draw is unavoidable. Some DACs also included some method of acting as a USB host itself (the Sound Blaster E5 for instance has a full sized USB port on it), but this again requires that the DAC now, at least to some extent, send power to the phone. Whether the phone or DAC is acting as a host, the big downside of this is that one device has to send power to the other device, even though both devices are independently powered by their own batteries.
While this didn't change when phones started utilizing USB-C, it did add some other options for how device-to-device connections could work without utilizing an OTG adapter (for instance, connecting two phones via type C and switching between either phone charging the other). A specific use case came from USB-C headphones, such as the ones that come bundled with many USB-C phones with no headphone jack now. One thing that I noticed when connecting USB-C headphones is that the usual USB mode menu doesn't pop up in the notification panel. Instead I get a quick, temporary notification when connecting or disconnecting the headphones. What I'm seeing is that when I connect the XD-05 to my phone with the included USB-C to USB-C cable, it behaves the exact same way. The permanent notification that pops up when either using an OTG adapter, or connecting to other USB-C devices via a standard USB-C cable is not present. Instead I get a quick notification when connecting or disconnecting. (Interestingly however, when I connect the cable alone, without the XD-05 connected, I do see this notification, however none of the options can be selected.)
What I believe is happening here is that xDuoo intentionally designed the XD-05 and its included cable to register as USB headphones do in Android to avoid the high power draw on the phone when utilizing a full USB-C connection, or acting as a USB host via an OTG adapter. This is most likely done via some sort of pin configuration (shorted/bridged/disconnected pins), much like how OTG is implemented, which causes Android to recognize the connected device as headphones (i.e. not proprietary). (To be clear, I've been specifically referring to active USB headphones that bypass the phone's DAC and receive a digital signal, and suggesting the XD-05 behaves the same way. Passive USB headphones rely on the phone's DAC and receive an analog signal. Clearly that's not ideal functionality for a DAC.)
The last piece of this is that it's not entirely true that other cables do not function at all with the XD-05. I've found that other cables will indeed work, but only if utilizing a proper OTG adapter. When you do so, as I mentioned above, your phone will act as a USB host and drain into the XD-05 a bit, but it's better than nothing (and its exactly how portable DACs worked before, so it's nothing new).
Finally, a quick disclaimer is required, since I'm by no means an expert on how the USB protocol works. As a tech enthusiast, I have a fairly good idea of how it works as well as a good amount of experience using it, and I've put this information together the best I can based on my understanding of it, but I very well could be wrong on some or all of this. If anyone knows better about any part of this, please feel free to correct me below.
Edited for some grammar, additional detail, and clarity.