The triangle balances naturally. You can independently fix or manipulate one or two of the sides, but the third is dependent and will adjust to balance. But this is not your problem.
Estimating is not your problem, either. You can estimate all day using all the tried and true leading estimating practices and it will not touch your dilemma.
There is a difference between an estimate, a target, and a planning value. An estimate is a probabilistic range, a target is what your customer or bosses may "dictate," and the planning value is a discrete value that lives somewhere on your estimate range, which can be optimistic, just right, or pessimistic.
Your issue is with the target. A target can live somewhere in the range, just like the planning value, but can also be a value no where near it, e.g., a number established as "price to win."
Your organization sounds very aggressive in its approach to win business. I would further suspect it is going into a piece of work with its eyes wide open, meaning they know what they are doing and they are accepting the associated risks and issues. Maybe their approach is using the initial contract as a loss leader, knowing they will certainly lose money on it but the relationship will lead to additional, more profitable business. I don't know their strategy, certainly, but I have seen this behavior more and more in very recent times, likely consistent with our current economical situation. After all, providing super planning values and estimates will do you no good if you lose the business to someone else.