Okay, so, a few things here.

First, for hardware sales, we don't actually push them. We started selling computers a long time ago, just as a service/convenience to our clients. It does add a bit to our bottom line but not enough to make us chase them, or to let us end up biased by our own sales. I even tell clients if I don't have channel pricing on a particular item and offer to give them a link to save a few bucks; half of them say not to bother and they'd rather just have me deal with it.

So, yeah, I don't care overly much if they don't buy from me.

That said, it is hugely annoying if they buy garbage and expect me to support it the same way I'd support the stuff I sell. If they go against my recommendations, I exclude support. If they buy garbage, no support. If they buy their own computers, I think they can process their own RMAs. My computers, I'll do the RMA. So we get paid either way. We either get the markup on the device or we get the billable labor if it doesn't work as advertised.

Finally, especially for stuff like network gear, we're billing the project install regardless and that is where our real margin is. I don't care if I miss out on a hundred bucks on some firewalls. I'm going to make quite a bit more on the configuration and installation.