IMHO it depends on both counts, everyone can probably cite a different example to prove their point. One that comes to mind for me: Pretty sure the RGT deal that a few people have referred to in this thread was basically sale price of $10 or $11 (my tractor supply receipt says $10.49) + tax with a $10 rebate, so basically $1-$3 net price for 5 quart jug. I've seen some pricing mistakes since I took advantage of that deal but don't recall sales plus rebate that have come to that price. Hard to say if $2/5qt. spent in 2020 is going to be equivalent or much worse when compared to the next sale that is going on when the oil gets used. Plus one has to find time to hunt for the deal when oil is needed (to be fair, could also argue some people spend tons of time hunting for deals too). My oil stash/hoard will last a while but (to state the obvious) I've had trouble getting as good of a price as I used to on some things like toilet paper and butter.
Realistically the stuff you see here is probably not impacting individual's personal bottom lines. The cost of acquisition is likely pretty low and for the equivalent dollars spent to appreciate, one has to take that money they would have spent on oil and invest it in something that is going to appreciate.