Selling B2B is "consultative," but there's a point where you need to turn the meter on.
The concept of "consultative" selling is that the sales professional should be adding value from the very start of the customer relationship. However, if that concept is taken too literally, you can end up providing free services to a prospect that never intends to buy.
This is particularly true when small companies are selling to large companies. People inside large companies often have only the vaguest notion of how businesses work. They think that budget dollars fall magically down the management chain and that everybody gets paid, whether work gets done or not.
When sales professionals from small companies sell to such behemoths, they're often asked to spend an enormous amount of time and effort to develop the customer relationship. In the worst cases, they're asked to provide entirely free services, even when the behemoth has no real intention of buying.
In fact, cynical corporate bureaucrats actually consider free labor from hopeful sales professionals as a viable cost-savings measure. I saw one example where a small software vendor developed detailed rollout and change management plans for a prospect, only to find out that the prospect planned from the start to buy from another vendor, but didn't want to pay that vendor for (guess what?) a detailed rollout and change management plan.
For sales professionals working in smaller firms, sales expert Bob Beck of Sales Builders recommends taking a "Quid Pro Quo" attitude and refuse to do ANYTHING -- even provide a brochure -- without insisting that the client do something in return (like getting a commitment for a face-to-face meeting with a decision-maker.)
Beyond that, if your actually selling your services, and your participation is important part of what you're selling, there's a point -- and it's not all that deep into the sales cycle -- where you've got to start getting the customer to pay for your services.
Let me put it this way. If you are truly capable of acting as a consultant and truly capable of adding value from the get-go, all the prospect should really need is a taste of what you have to offer. Keep up the free consulting past that point and there's good chance that you're just being taken for a ride.
UPDATE (4/23): An example of how to avoid "consulting for free" is provided at "How Quid Pro Quo Selling Works."