Contract clauses that state that upon some event (like a change in costs of supplies) the price charged under the contract will be (re) negotiated in good faith may not be binding. These clauses are sometimes inserted into contracts so that contingencies may be addressed in an even-handed way, while still keeping a binding contract in place between the parties. However, in some circumstances, such clauses will be held by a Court to simply be another version of a non-binding “agreement to agree.”
Whether the clause is enforceable depends on whether other major terms of the contract are agreed to, and also whether there is some objective basis or standard governing the so-called good faith (re)-negotiation. The clause may be enforceable when there is sufficient certainty regarding the issue or issues to be negotiated in good faith.
This appears to be solid law in Canada, upheld in a number of decisions including Molson Canada v. Miller Brewing 2013 Ontario Superior Court, the House of Lords decision Wolford v. Miles, Empress Towers v. BNS, and TDL Group v. DXStorm.com.