Supply and demand, I suppose. For those whose primary music source is optical disc, it was the best sounding of the Oppo disc players (I owned most every version Oppo made) for those discs it could play, which was most.
The earlier 105D was actually the most versatile player Oppo ever made, however, since it provided access to many streaming services (including Tidal) and decoded HDCD discs, two things the UDP-205 could not do. Late in the production run Oppo added MQA decoding to the UDP-205, however, so if you had fed a streamer into its USB audio jack, the 205's DAC would provide full MQA decoding out of the Oppo's analog outputs. I did not think it did a very good job of that, however, preferring the Auralic Aries G2's MQA decoding (even though it was not a licensed MQA decoder), and my current Lumin X1 has far superior MQA sound.
In addition, the UDP-205 is one of the best DVD and Blu-Ray players in terms of video quality, at least up through the 4k video standard.
The choices Oppo made in dropping HDCD decoding and direct access to streaming services were probably market driven. Most of the best recent DA chips don't handle HDCD decoding. And since there are software programs (such as dB Poweramp) which decode HDCD when you rip the disc to a file, you could feed the 205 computer audio files already decoded from your networked hard drive. As to streaming services, today those have migrated to dedicated streamers or to receivers and amps. If you want to, you can feed the digital output of a computer or streamer into the Oppo's digital audio inputs and let the 205's DAC decode the stream.
Today, I would not buy the UDP-205 at these inflated prices. I've moved on, as have many or most, to sourcing music from computer files on my local network or from internet streaming services. Today, the Lumin X1, fed from my network computer and internet, is the only audio source box I need in my greatly simplified audio system. The Lumin has a volume control so it acts as my "preamp" and directly feeds my amps, which drive my speakers.