Per Mbps Pricing

I am working with one of the new DCs that we deal with to negotiate some colo pricing and setups. They are not huge on colo, in fact they do very little of it. Hard to believe out of about 1200 servers in their DC, their colo section will not even fill 2 to 3 racks.

They do not even have a setup to price based on per Mbps, I'm sure they know about where they need to be if they dig into it, but they want me to work up a proposal based on what I need (they are working hard to work with me and keep our business).

Their network is fine, nothing outstanding but plenty strong for our needs.

They use mostly Time Warner and Level 3. I think I can even setup with them to provide my own rack, which I prefer to do since it would keep only our servers in the rack.

My question is, from those who have plenty experience on different levels at different Mbps pricing, what is average and reasonable considering those 2 carriers? If I provide a rack, they will provide power, UPS, etc. Aside from that, I need advice on what to expect on the pricing of the bandwidth.

I may also end up using my own Cisco switch in the rack, I haven't cleared that up yet.
If I start off @ 10 Mbps in the rack, and work up, about where should this be on BW pricing?