I'm fairly sure that the new controller uses TMR instead of Hall Effect joysticks. 

My guess is 80 USD. 

I bought a 8 bitdo ult 2 and a 2 c both are great. My only problem is that I wished that the USB stick support multiple controls like the 8 controllers thr Xbox wireless adapter. 

1 dollar, Bob.

I'm thinking the right price is about $80, and I'd be very happy if the price is lower than that.

I'd consider at top $100. One should come with the Steam Machine right? It can't be too expensive to manufacture if it's coming with what should be a competitively priced PC

That seems a bit high high to me; if they want to move them in significant quantities, I'd think they'd need to try to land in the $80 USD range, give or take a hair.

They have quite a few other controller options out there that they are competing against, and even though it's awesome, they definitely could potentially price people off of it.

The 8Bit-Do Ultimate 2 with TMR-Sticks and Backbuttons was just over 55€ before christmas. Those features don't necessarily mean a steep pricetag.

the price of a General controller with back buttons and no Hall effect Joysticks or touchpads is already about 100€

That seems expensive, you can get hall effect or even TMR sticks and back buttons for well below that. That said, I do think the Steam Controller will be more expensive than that. 80-100€ is my guess.

$3.50

$100

Would you buy these if you have a steam deck? If so, why

If a steam controller 2 or whatever is in the ballpark of around $100USD, I'd be down to either save for one or hope Valve does something similar to what they did with the steam deck and sell refurbished controllers at a slightly lower price.

$2