This is an example of why I feel it is very helpful to have a spare vehicle, at least 1 more than # of drivers at a residence, so if you have to suffer extended downtime, nobody is without transportation. Granted if it's a work truck or whatever, what that extra vehicle is has to be more carefully considered.
I too, sometimes get frustrated with Rock Auto but often their prices can't be beat if you want to spend the time to make a list of soon needed items and can get them from one warehouse, they when you need things from a different warehouse, you have a multi-item list for that as well.
Overall Amazon gets things to me faster but I too have seen their Prime 2 day take longer than 2 days, but more annoying is when I didn't have Prime and placed an order, they'd SIT on the order for several days to make sure it took way longer than prime would have... once they finally get the order out, it only took 2-3 days to get here but by sitting on the order, they made sure it took at least an extra 3 business days.
They did then meet their estimated ship date but something rubs me wrong about deliberately delaying to ship an order, if it were just them paying for a cheaper shipping method that would be different and the normal thing any other merchant does.
Regardless, RA and Amazon tend to be the two lowest cost options. Some things I will just buy locally instead, particularly from a very nearby Autozone because Autozone has more items with a lifetime warranty backed by them rather than through mail back to a manufacturer or seller/distributor... but usually, that part with a lifetime warranty is going to cost at least 40% more than the extact same (or same quality level at least) item from RA or Amazon.
I used to shop most at NAPA back in the day, they tended to have the highest quality in stock parts locally, but it is further away and meh my purposes are usually as above, lower cost for my pick of quality, or lifetime warranty and get it from Autozone two miles up the road.