I can give you an estimate for my old organization back in Guj land: 512 kbps leased line for 66lakhs annually(heavily negotiated rates at that). That also included a VPN to our main gateway located some 250km away, whose internet costs were separate.
That being said, please do plan for redundant connections. I would anyday recommend even three peer connections with a big fat linux quad core server acting as the gateway and managing bandwidth. Our leased line used to be down more than once a month (You Telecom) and without redundancy, life was a pain. I personally believe (i'm no network specialist here) that with three redundant ADSL connections (say Airtel 512, Tata 512 etc), you'd be paying some 30-40k a month for way better speeds than a 512 leased line.
VSNL rules in general, but in DSL, they are complete idiots - they give true speeds (true 128 not a fraction like airtel guys sometimes find), but if the link goes down, then its usual inefficiencies come to fore. I had a unltd connection for 6 months, not one hour of downtime - a friend bought it on my recommendation - was down more than 50% of the time - but that's residential. I'd hope they would give better service for commercial buyers. |