Some businesses might as well lower their standards because it is their business model, and sell their product/service cheap, with a quality so low that it can be quite surprising. If you want to do the same with yours that is your call, but know up to what point what you are selling can be cheapened, and to what point you will be selling short not only your product or service, but what you or the company behind it envisioned when conceiving it. It’s all about principles.
Also, at times it might not even be about price alone, but others cards at play: if you conduct an ethical business, great deals with unethical companies might be selling your product/service short. If you are conducting business for a company proud of its high social responsibility standards, and find yourself negotiating with a company known for being on the other side of such field, it might be even worse than selling below the price principle. Price is one of the variables involved, and principles go way beyond a simple matter of money.
Just as you have principles on your personal life, business you conduct should have theirs as well: is it the lower quality one that can be sold really cheap, or is it the higher standards one? Never lower your standards because of clients’ pressure, more than your principles allow, for it may be impossible to go back. Know your negotiation window, and if the focus in place is simply being the cheapest, or aiming to be the best (on all parts of the business).