Hi. The starting price is $4,295 in the US for delivery and set up. You will also need to pay a monthly subscription of $39/month. If you already pay a monthly subscription for the bike you don't need a second one to use the tread and you would be able to use the tread and bike at the same time. There are packages with accessories but I would recommend buying those separately (weights, headphones, mat, etc.) from somewhere else as you will find similar products that are cheaper and/or better quality.
People who own the tread seem to love it so although it's expensive if you use it regularly it can be a good investment. I've tried it and it's a great treadmill with excellent interactive features like the bike. One thing to note is that it's pretty large so you need a decent space for it.
If you buy one make sure to use a referral code which you can get from any owner so you get $100 off accessories.