I heard on the news that Costco is limiting purchase of motor oil

I totally agree, there has been plenty of times when I couldn’t afford to pay out big chunks at a time, so it was much easier to pay $200 a month than it was to take a hit of $900 twice a year as an example, even if it saved a few $$…
Same reason a lot of/most people pay for their vehicles over time rather than all up front…

But some people would rather have all of their bills come monthly, regardless of how big or small their budget is…

Personally, I HATE having payouts or bills that are paid months—or even a year—in advance… I think the only big bills that my household and my mom’s household have that aren’t monthly are our city and county taxes, which come once a year… We do have a few smaller, nitpicky yearly expenses, like subscriptions, but for the most part, we keep things monthly…

Back on topic, I use the Kirkland oil in my vehicles. A few months ago it $38 for two 5 quart jugs and would sometimes go on sale for about $32. I noticed last week that it is now $57. I guess it will be a long time before I see it on sale for $32.

BTW the Mobil one oil is still $37 for a six pack, I expect that it will jump soon.

They don’t have wholesale supplier that’s cheaper?

Some garages are too small for the wholesale supplier OR they aren’t in good standings with the supplier (more likely) and the supplier won’t deal with them.