Point of higher priced streamer?

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.

All the streamer does is deliver the packets to the DAC.

How do you think the packets get there?  Via electrical signal of course...so therein lies the opportunity for sonic degradation or improvement by better design

With this said, I do agree with @mapman that it's all about prioritizing your spend and where you get the most bang for your buck.  A streamer upgrade is not the first place I'd look to allocate funds towards improving sound, but when I finally started running out of areas to improve I finally went to the streamer.

How do you think the packets get there? Via electrical signal of course...so therein lies the opportunity for sonic degradation or improvement by better design.

No not really. The signal arrives intact or not. The DAC is able to reconstruct or not. Did this post make it in one piece or is every other letter missing?