Re: per month per Mbps to 28 euro cents
> I assume it covers the cost of routing data to the rest of the world ...
Then you assume wrong.
Think of a room with a big ethernet switch in it. Various ISPs, transit providers, etc get their own connections to that room and plug into the big switch. All these outfits can then make arrangements to "peer" with each other - effectively "I'll take your traffic if you'll take mine" or "I'll pay you to take my traffic across the Atlantic" arrangements.
The advantage over peer-peer connections is the scalability. If you have 3 providers that want to peer, that's three links (A-B, B-C, and A-C), for 4 providers you need 6 links (A-B, A-C, A-D, B-C, B-D, C-D), and when you get to the dozens or hundreds of outfits in the market these days, the number of provider to provider links would be huge - and very expensive.
Alternatively, the ISPs would have to send their traffic "up" to a transit provider who would then route it back "down" to the peer - at a cost.
So they all get one connection to a single exchange - one link for provider A, one link for B, and so on. They can all talk to each other via this "big switch".
As an analogy, suppose you are one of hundreds of companies in big office block. And lets suppose that you do a certain amount of business with other companies - you might be doing IT for them, others are doing HR or secretarial or accounting for you, and so on. You can have someone walk round the building to deliver post to others you deal with (roughly analogous to peer to peer connections), or you can stick stamps on the envelopes and get BT to route them via the nearest sorting office (roughly analogous to sending the traffic up to transit networks), or you can all send someone down to the post room and drop the letters in the post boxes for the other companies - this is roughly equivalent to an IXP, a "Post room for the internet".