I'm pretty sure this is completely off-topic here, but anyway...
You seem to be mixing up a lot of things.
First, there's a difference between technology and actually providing a service. A company could introduce a new technology that could be used for last-mile access, but not actually provide any services, opting to sell the technology to telecommunications companies.
Next, though that's unlikely in the current environment, a company may opt to provide telecommunications services, but not actually become an ISP, opting to resell the last-mile access to actual ISPs. Note that in other contexts, this actually happens in many markets (mostly in Europe) where incumbents (the former state monopolies) are forced to resell use of their last-mile network (which was in most cases publicly funded) to competitors.
Then, if a company decides to actually become an ISP in its own right, they need to ensure they have connectivity to the rest of the Internet. This takes two forms: peering (which gives access only to the other network's customers) and transit, which will give you access to your transit provider's customers, peers and upstream transit, resulting in access to all of the Internet.
Peering may occur at Internet eXchange (IX) points, or be arranged as private peering (which may happen at IXs, other colocation facilities, or even via dedicated circuits between the two ISPs). Historically, peering was free, but nowadays there's a mix of free and paid peering, and peering policies are a complex beast (most ISPs only want to peer with ISPs that have a similar or larger size, and similar traffic patterns).
A so-called "Tier 1" ISP is an ISP that does not buy transit. There's a handful of them, which for historical reasons have always peered with each other. All other ISPs are (directly or indirectly) customers of one or more of those ISPs.
The cost of transit is just a commercial negotiation like any other. It's very similar to a end user picking their ISP or cell phone provider. Negotiation includes speed, connection points, service guarantees, etc. Most serious ISPs are "multi-homed", which means they buy transit from several "upstream" ISPs. They also try to have as much (free) peering traffic as possible.
There's a lot of competition in this field, so new ISPs have a wide choice of options, and there's very little regulation. If you want details of regulations, you'll have to specify which markets you are talking about.
On a side note, wireless last mile is nothing new, and comes with its own challenges, including deployment of base stations, spectrum use, line-of-sight/coverage, etc. It's definitely not the magical solution some would like to pretend it is.