I check the prices at the time of my order, and factor in the cost of shipping. I tend to buy from the best/least expensive source available at the time of my order. However, making a large purchase when I can get the best price, has helped prevent me from having to scramble for a good price later. I don't buy it in buckets, however, as for my needs that doesn't make sense.
Essential Depot has periodic promotions that offer free shipping. AND they also have periodic sales on their NaOH. Both those times make for phenomenal price reductions, and that's when I buy from ED. I prefer the ED lye bottles because they are MOST suitable (for me) for holding my masterbatch lye solution, so that is an added plus when I buy from them.
A couple of other times, I have purchased from an Amazon vendor at a pretty low price and no additional shipping. When that price is the best at the time of my order, that's where I buy.
I have used Lye Guy NaOH, but did not like the PET plastic bottles it came in; safe enough for dry lye, but a bit too flimsy for my liking. Plus the cost of shipping for me made the bottom line price too high anyway.
Other online vendors I have used, but ruled out due to the high cost of shipping to my location were Bulk Apothecary, Bramble Berry and most others I have included in my pricing checks.