As far as the cheapskates I do weed them out here too. Just can't afford to waste my time with them beside most are buying from eBay anyways and wanting me to install the parts for free. That doesn't pay my bills nor put food on the table.
When it come to markups it is a lot easier now for me to load the distributor provided price files with mods whenever needed. Most have reasonable shipping that their prices account for. I do however have one distributor that have higher shipping cost; unless, I order $200+ so I have to add a 10% GPM to their list prices in the price files to help the shipping. Loading price files makes it a lot easier to to reprice 150,000+ part numbers along with adding all the supersedes. Currently I have 761,000 + SKU (part numbers) load on to my computer via the price files. The only drawback is that it takes me a few days to convert the file to format my system will import correctly.
I am beginning to get a handle on that one distributor so they are going to hate my just over $200 orders. Just received a $200.25 order where they had to write-off $45 in shipping charges. So I ended up something I didn't need right a way but well worth it so I didn't have to pay the $45. That was the best 0.50 I have spent in a while.