Indeed, this is how bandwidth is sold.
To get an idea of how much $300/mo is, I just had a quote for a 1 gig dedicated ethernet from our office (not a datacentre) in Delhi to our rack in Telehouse Docklands North for $18k a month, or $18/mbit. For datacentre-datacentre I had a quote from Seoul KINX for $5k/month, or $5/mbit. Layer 2 links in both cases. These are fairly long haul links.