Support is any time someone calls you about the product you sold them.
It could be tech support or if a part fails product support. Some States, like California, the end seller is responsible to honor the product warranty. Unless that is if you sell "as is, no warranty". But what kind of business does that? I'll tell you, none that plans to stay in business very long. You could only provide Labor and let or tell the customer supply the parts but there goes profit out the window.
$100 for building (mild OC if they want, includes P95 testing 8+hrs) + $100-150 for liquid cooling, mods,etc. Free labor on CPU/GPU upgrades for 3 years. I don't provide software support, but do warrant hardware defects.