As a consultant, I advise my clients to look at a lot more than price when selecting an integrator. Experience with similar projects using similar products is very important to me, as well as the depth of the integrator's overall project team. Good references and the integrator's demonstrated track record in solving problems when things go wrong are also big factors in my recommendations to the client. (All integrators look good when things go well, the real test of an integrator for me is how well they respond when things go badly. In many cases, this is due to no fault of their own, such as a bad product from a manufacturer.)
In many cases, I can convince a client to pay a 15% to 20% premium to get a more qualified integrator. But if the price difference is higher, it is difficult to convince the client to select the higher-priced integrator no matter how qualified he or she is. In public works projects, usually the client's hands are tied - he must choose the lowest bid unless there is material proof that the low bidder is unqualified or has made a major mistake.
Sometimes (believe it or not) the client chooses to ignore my advice completely and selects the low bidder or someone he has a previous relationship with. Remember that in most cases, the client, not the consultant, makes the final decisions.
When I specify a specific product or group of products in a specification, integrator's need to understand that this is not something I pull out of the air - the decision is usually based on many weeks or months of product research, visits to existing sites where the product is installed, and factory product demonstrations with client representatives. At this late stage in the process, final decisions have already been made, and we are generally not willing to entertain other products or design approaches.
That being said, I often allow bidders to submit two proposals: one that fully complies with my specifications, and a second that utilizes alternative products or a different design approach suggested by the bidder. Within this second proposal, a strong case needs to be made as to why this alternative proposal benefits the client. Being significantly less expensive usually always gets the attention of the client, but other benefits can sometimes tip the scales as well. Alternative proposals that benefit only the bidder (Milestone is specified but the integrator sells only Exacq so proposes it instead) are rarely successful.
I discuss this topic in more detail in my article How Security Integrators Can Succeed Working With Consultants