Point of higher priced streamer?

All the streamer does is deliver the packets to the DAC. It's purpose no more affects the packets of audio data than the miles of cables, myriad of switches and routers affects the packets delivering this post from my keyboard to your screen. Sangbro just get whatever streamer that has the options you want and forget about it. I've  used streamers from raspberry pi4 to Lumin, Bel Canto, Auurender, Auralic and others not a dimes worth of difference when level matched .

Yes, It’s called expectation bias. The same phenomenon that largely drives the high end cable market. That and listeners neglecting to level-match when conducting comparisons.

That's is an extremely wide brush to use to simply dismiss differences that many folks hear, myself included.   

I've been using a RaspPi (running Roon) with a Digi+ SPDIF interface and iFi power supply as my primary streamer for years.  I recently spent less on a new DAC than I was expecting (because the most expensive one and it also has the most brand cachet didn't sound as good as I was expecting); I settled on an an R2R NOS DAC that costs considerably less but to me sounds better.

I then decided to spend the extra $$ on a better streamer to see if I could hear a difference, knowing I could flip the streamer (a Bricasti M5) easily if it wasn't worth it.  It made a significant difference in my system that I'm now disappointed I didn't try a better streamer years ago.   And yes, I have a sound meter (my trusty old analog Radio Shack meter).   So no, I don't buy your expectation bias or level-matching argument for my scenario.  I choose what sounds best to me and gives me the most musical enjoyment, working within my budget.

There is no doubt in my mind the Pi with a good quality SPDIF board is an excellent audio value relatively speaking, but in absolute terms in my system and using my ears, the M5 takes my listening enjoyment to another level and the difference in cost is more than worth it to me.   If the Pi sounds the same or better than the M5 to some folks in their system, then they should be happy they are saving some money, but that doesn't change the fact I prefer its sound quality more and am willing to pay for it...

OP,
Steamer upgrades made a difference in my system. My A/B testing were double blind with friends as test subjects. I used to be a skeptic about streamers - trying to understand how a streamer could possibly make a difference above and beyond Sonos and Bluesound - I mean my SQ was already tremendous.

But then I took a risk and purchased a better streamer (more expensive) and it was a very significant upgrade for me. Yes, I then purchased an even more expensive Streamer and there was still a noticeable SQ uptick (more openness, more immersion in sound - would be the best way to summarize it) The difference was almost the same as when I upgraded my Denon SACD player to an entry level Esoteric SACD player and then to higher- end Esoteric SACD player - with different levels of improvements along the way.

I could go on about the differences in SQ (or why I think there are differences), but could you perhaps describe your system in some detail?  It would be helpful to know this in order to better answer your original question.  Because - yes, in some (many) cases, upgrading to a more expensive component (steamer) may make no difference within a particular system - most of the time it depends on the rest of the chain.
Regards.

I’m not saying streamers can’t make a difference.  Obviously they can. Only that in practice I have not found them to be a big factor compared to the other usual culprits.  So at best a streamer upgrade alone is one of the last things I would consider.  I just find that when things are going well most any good quality streamer will do.    

@sangbro 

Assuming I have separate DAC, and I just want to play songs from iPad by Airplay feature.
In this case, I need a streamer to receive music from my iPad -> DAC.

If this is really your goal, "play songs from iPad by AirPlay", you may want to consider just getting a quality bluetooth receiver. You can connect from your iPad to the bluetooth receiver and play anything that you can play directly on your iPad. 

I have the Auris BluMe HD bluetooth receiver and find it to be very good. It costs just over $100 direct from Auris and I believe they have a return policy. It does have a built-in DAC, but it also has a toslink optical digital output if you choose to use an external DAC. I have mine connected via RCA analog connections and via toslink digital connection to my DAC and I hear only minor differences in my warmish sounding (not highly resolving) 2-Channel Audio System.

If you're unsure about the value of a dedicated streamer, and just want to listen to songs played from your iPad on your audio system, you might want to just give a quality bluetooth receiver a try. Certainly doesn't cost much. Oh, and my understanding is that the old, original Chromecast Audio was surprisingly good too. You can find used Chromecast Audio (only the dedicated Chromecast Audio, not the plan Chromecast) for around $50 on eBay. That might work for you too, although I have never tried it myself.