One thing I learned early on in business is: it's always easier to lower your prices than to raise them, so set your initial valuation high; you can always drop it later if you need to.
In the enterprise space, I have learned that if you drop your price for one customer, your other customers will quickly learn of the new "price floor."
While I don't deal with enterprise sales, I do security consulting for the enterprise, and one thing I do is never lower my prices. Instead, I'll just add additional value over top, e.g. an extra day of consulting. Yes, it has the same effect for me, but it doesn't get my clients in the habit of paying me less money.
Everyone likes getting something "for free". For an enterprise-level customer, another day of consulting. For smaller customers, a free t-shirt or water bottle. Goes back to the whole perceived-value thing.
No, you bill at the level your contract states that you charge. Doesn't matter what you have anyone else pay you it's what you negotiated through the bidding/negotiation process.
Usually the enterprise sales process will include a confidentiality agreement which includes the sale price, discounts, etc for that customer. Usually this is enough for most transactions.
The medical equipment company I used to work for had a price for its gear that included a starting discount of 5% for any sale, to make the customer feel like they're getting a good deal.
