Verizon used to claim "half of all Internet messages pass through our network." That's unlikely today, as several carriers have networks as global as what Verizon built after acquiring UUNet. There are many ways to measure size of backbone providers, but this chart from Telegeography is highly suggestive. Level 3/CenturyLink, Orange, and AT&T most frequently offer Direct Internet Access in165 global metros. Cogent, Sprint, Tata, and Deutsche Telekom also are found in more places than Verizon. NTT and BT follow.
Their colleague, Brianna Boudreau, separately looked at the trend in international bandwidth costs. https://blog.telegeography.com/global-bandwidth-prices-are-converging-somewhat
"Across critical global routes, weighted median 10 Gbps and 100 Gbps prices fell an average of 14% and 23% compounded annually since 2016. ... 100 Gbps cost 4.3 times 10 Gbps while delivering 10 times the capacity."
Huge disparities continue. 10 Gbps from Los Angeles to Tokyo (5500 miles) costs ~US$5,000. Los Angeles to Sydney is about 40% further (7500 miles) but costs more than three times as much. I've reported the disparities to Africa are even higher; the cartel-like pricing of transit and backhaul is the largest international factor in high African Internet prices.
Greg Bryan and Elizabeth Thorne used Telegeography data to look at pricing. They found that the largest (Tier 1) carriers did not usually charge more than the slightly smaller ones for DIA. In a separate article, Thorne calculated the savings of several switches from carrier MPLS to an SD-WAN. In her models, informed by research into actual pricing, the savings were ~50%.
Here, the bandwidth pricing and DIA deployment data from Telegeography, a respected source.