I order the ESP from NAPA and they have it the next day. Typically I'll buy a full years worth, or more, and replenish what I use every 6-9 months. So at least for me them not having it in stock is not an issue. If I place an order early enough they often have it a few hours later. If I have to buy oil online or order it, odds are I'll be waiting a lot longer than getting it from NAPA.That is why I said regular price. Amsoil also has some deals.
Problem with ESP at NAPA, at least in my area is that they do not stock it.
Final thoughts: I only buy ESP on sale, and try to time it with a rebate. Having a small stash helps in doing that.