It's not crazy expensive, but it was always cost prohibitive to us at Fluid since there were way better things to spend money on, IMHO.
I can try and break it down for you if you want.
First of all you need enough analog outputs to make it work. I would say 8 channels would be a good starting point. You would rely more on submixes, but if you wanted to go for 16 then you need more free channels and a hub capable of of handling 16 channels as well. So let's do both secenarios:
8 Channel -
Hear Back - 4pk -
~$2000.
This system would be a basic entry point that wouldn't break the bank. It comes with 4 personal mixers, but the hub can accommodate 8 mixers in total. Each additional
personal mixer would cost you about an extra $300. Cabling is easy enough to deal with since it is just ethernet cable, which is cheap and you can make it whatever length you want to accommodate player position. All you need is 8 spare channels from your DA and you are golden.
16 Channel -
Aviom AN-16/i v.2 + 4 Mixers -
~$4000.
This system would be more expensive (in total) but also more expandable and probably would lead to a better end-user experience. The hub itself is about $1200, but right off the bat you would have to buy the
personal mixers seperately which are normally $500ea, but sweetwater is having a sale on them bring it down to $400ea. You would also potentially want to buy a
distribution hub to avoid having to daisy chain your personal mixers. So all said and done for a proper system with 4 mixers you are nearly at $4000, not including the extra channels of DA you'd need (if you don't already have 16 spare channels of DA laying around...)
Hope this helps!