the $10 a box stuff is just fmj/ball ammo and not meant for hunting.
the hunting stuff is supposed to end up around $20ish a box. pretty much right on par with most hunting ammo these days.
its definitely caught my eye, although i'm leaning towards an AR upper and not a bolt gun... but thats personal preference and not much else coming into play there.
its a very much purpose engineered caliber targeted at states that have recently opened up what has been historically shotgun-only deer hunting to straight walled rifle cartridges. Michigan, ohio, illinois, idaho are just a couple that come to mind right off the gate.
there are of course other cartridges being used int hose states already - and i'd say that 450 bushmaster is probably been the king of the cornfields so far. but much like the 50 beowulf - it comes with its well earned nickname of "thumper" due to the recoil those heavy/larger caliber offerings come with.
so Winchester really did go smart with this release iMHO - i think its got the potential to take off like wildfire for the following reasons
1) its supposed to be mild on recoil compared to the other usual suspects that are legal in these restricted hunting zones. not shocking that a 150gr 35 caliber bullet is going to have less punch than a 45 or 50 caliber offering at upto 2x that weight class. that means more people are going to be able to handle it - including youth, women & older hunters. It also means people wont be as shy of practicing with it because those who dont know how to handle recoil dont need to learn to do so to shoot the caliber.
2)they offered affordable practice ammunition right from the start. as you noted $10 a box fmj practice ammo... winning!
3) they use the same brass cups that 223 is formed from, but it requires an extra forming step to get the slightly larger OD necessary for the cartridge. So while you cant just convert 223 range pickup brass at home, the base product for making the brass commercially is plentiful and affordable. so the barrier to production at reasonable prices is low to start.
4) by using the standard 223 case rim dimensions - they have readily available bolt faces that are designed to withstand >60,000 PSI cartridges. The same applies to the action... take a standard action and thread the right barrel in and you're in business. minimal magazine modification necessary (if any at all). etc. pretty much Plug and play for the engineers.
5) 35 caliber bullets are a known thing and selecting one for use - especailly looking at the plinking stuff - probably didnt require much, if any, engineering at all. probably the only other caliber with more choices would be .308 dia 30 cal....
6) "everyone" knows that a 150gr bullet at 23xx fps will kill a deer handily. if a 30-30 can do it, a 35 caliber of the same speed/weight [beeep] well better be able to. and the 30-30 is a known deer slayer in north america - [beeep] its probably put more venison on the dinner plate than about any caliber out there.
all in all - as i said, i think its a recipe for quick adoption and potential long term success in the hunting world.