Well I wouldn't expect their world to exactly collide with the CI world particularly. Hey never hurts to ask for a cash discount....it's mandatory in some (most?) parts of the world to do some bargaining (altho I also come from the old murican school of I said my price now take it or leave it

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Checks bounce, cash (if it's not counterfeit) doesn't. While making someone a target for robbery, cash is pretty safe but at the time, taking checks cost a fair amount of money, especially when they did bounce and the one who passed it can't be found. Now, I'll take a check without hesitation because I can deposit it using the app in my phone but as someone who often takes large payments, I prefer checks.
A retailer has every right to set a price and not take a penny less. Gouging, OTOH, is something I really hate and when people do that, it just shows their level of greed. They usually spout the Econ 101 definition of setting price by saying "It's what the market will bear". Maybe, if they can find more rubes who'll pay an exorbitant amount, but one customer doth not a market make.
CI people run into all kinds of customers who want to save money but as I posted before, working with a large number of brands makes someone a generalist, not a specialist and when things become overly technical, a specialist is what's needed, not some Craig's List guy who'll do a hang & bang for $50.
People also have every right to buy what they want, at a price that works for them and I understand that well- the problem they're likely to face is in finding someone who's willing to do the work and have the conversations that result from customer-sourced equipment that may not work. I have do that and it sucks because the customer usually tries to blame the next guy (it worked before YOU touched it!)- this can sometimes be averted by making the customer demonstrate the equipment in use before starting the job. I saw this a lot when I worked with car audio. Also, most auto repair shops won't use customer-sourced parts and if they do, they won't guarantee the repairs.
Dickering is fine, but at some point, it often becomes insulting to the seller. People like to think they know the seller's cost, but they NEVER consider all of the expenses. Part of what now makes selling AV is that more manufacturers are making it easier for end users to buy direct, on the manufacturer's website. That wouldn't be so bad if their prices made it possible for us to compete with them, but they're often lower than a dealer may pay. That's a slap in the face for us because when a brand has recurring problems, we're the ones who are supporting them by removing, reinstalling, reprogramming and explaining that "it's really a good brand, but they're having a problem".
Some companies, like Sonos, will harvest user info and market directly to them, after WE made the sale, installed the equipment & made it work when THEY constantly ignore our requests for additional functions and connections but never respond. WE made Sonos successful by supporting them when people would hear the name and respond with "Who?".
OTOH, that can lead to opportunities, like the one I had when I received a call from someone who had bought Sonos direct and the other dealer decided they didn't want to install it. She had gone to the dealer to look at it and when she checked her e-mail, saw an offer for a 35% discount, direct from Sonos. If they only knew what they actually needed to do for this stuff to work properly, they may not have declined because it wasn't just 'open the boxes and set up some Sonos', they needed wired network connections, a couple of network switches, moving the router, doing some router setup and other work. This is one of the reasons I like having long-term clientele- I have some control over what I install and they come back the next time because the equipment tends to work for a long time, so they refer others to me (like the woman with the Sonos).