How does making it cheaper suddenly make it exceptable or some how fix the error.
I have struck this problem in the past. It is either exceptable or it is not. In the past I have done the job again, but I will not compromise on the price (Signwise Central Coast, James Smith) 

Tell them to bugger off. Especially as you would hope that the spec and your soft proof was signed off on prior to printing. There's a fine line between going overboard on customer satisfaction and being a successful long term business. If you let that one through to the keeper then you are making a rod for your own back. (Bigprints Pty Ltd. Rob Matthews) 

You say: "mate, you signed the quote form I gave you, you signed the artwork approval form I gave you, I have been as clear, honest and transparent as I can be, please show me the same respect". 

I do not tolerate clients who default on their commitment to pay for work done, I start legal proceedings ASAP. I do not start work without a signed approval to go ahead after producing a proof of the required work. If they do not like my price they can go and get (f^*#@d) it done elsewhere (without the proof I have produced). (Geraldton GraFX Signs, Bernie)

This is a common way for clients to avoid payment, what I say is, it will be cheaper if you pay the agreed confirmed price now. Because if I end up taking you to court it WILL cost you double..

Generally we refer them back to the quote that they have signed off on and the artwork approval form they have signed. Depending on the type of client and existing relationship we will either enforce payment, by debt collection if necessary. Or come to some sort of compromise to maintain goodwill. If the client is continously difficult we will relegate them to bad client status and insist on a deposit up front or full payment upfront or on completion/pickup. Business is a long term venture so ongoing relationship and reputation need to be factored in before you go too hardcore in the beginning. (Qld Signage Solutions, Wal Robinson)

Firstly I would ascertain the actual issue he has with the job. If a small rectification can be made to make him happy I would do it. If he persists he wants a price decrease and not any type of rectification I would class this type of client as a "D" rated client as he probably had this tactic in mind from the start. I would make sure that all our systems and procedures were followed correctly, from the initial consultation, design, quoting and proofing and production so that he "the Client" at all stages had approved and understood before commencing to the next stage. If all checks and balances are fine then I would politely remind him that at all stages of the production he had approved and did not raise any concerns on the project. I would show him the signed copies including the quoted price approval. Then I would politely request payment as we have deliver exactly what was requested to the price approved. If he still refuse to pay I would not waist any time chasing payment I would just hand the account over to our debt collection agency and begin debt recovery proceedings. Needless to say he would be cash up front after that.... ( Steve Baker Signs Pty Ltd.  Steve Baker)

A good question. Most printers I speak with say it is common for a quote to be given only to find that additional processes are needed - eg lamination, die-cutting, special colours or metallics etc. It is vital to re-quote for these value-adds and not 'throw them in.' Best quote from an old printer friend when asked for a much cheaper price: "Why should I spend time losing money on your order when I am busy making money on several others?"

80 % of your profits come from 20% of your clients and 80% of your problems come from different 20% of your clients. Time to figure out which clients you want and which clients to advise to visit your opposition so they can enjoy the problem. This only happens with mismatched expectations and poor communication, not explaining what was going to be delivered and how payment within terms is required. Not a lot of sympathy if this ever happens.

I can't recall the last time this happened, these days we have online proof approvals, T&Cs, deposits and prepayments to avoid these situations.

It has been my experience that they can only beat you down on price if you haven't fully disclosed the nature of the work from the quality to the stock it is printed on. Always describe what you are providing in detail and don't discount! ( Kwik Kopy Phillip, Emilio)

It does not happen often but it probably does happen at some stage in a business. As long as you have a signed proof and quote and provided you are certain you are in the right, then sue the pants of the individual or company. The mere threat of legal action could bring them to their senses. Of course black list them for any fture business.