Ranges observed across our catalog: 1 Gbps: 150–400 €/month · 10 Gbps: 420–950 €/month. Above that (25/40/100 Gbps), pricing is negotiated case by case but the per-megabit cost keeps falling sharply.
What moves the price: the carrier density of the data center (competition in the meet-me room drives prices down — the #1 criterion), the commitment (12/24/36 months), the billing mode (full port vs 95th percentile with commit), and options: DDoS protection included or not, BGP sessions, IPv4 blocks provided (2–3 €/IP/month).
Don’t forget the access cost: a cross-connect to the carrier at each end.