Well, the costs for shipping of one resistor is pretty steep in comparison to the price of the part, I'll agree. OTOH, I buy in bulk, so shipping is not a major part of the price. I don't see any local places around me that have any assortment of electronic components, so it's either mail-order or nothing.
One way you can minimize the issue of going for "one" capacitor or resistor is to buy an assortment. There are tons of resistor and capacitor assortments available for a few bucks, that gives you readily available parts in most common values.
. . . and therein lies the problem -- to solve almost *anything* electronic, it seems you need either ready access to retail-level components, *or* you need to start stocking up like you're about to open one of the (late, lamented) RS stores, with heaps of spare parts and a lot of salvaged scrap. Hey, I've already slid down enough rabbit holes after finding and resurrecting my childhood Marx train set's rolling stock -- I can't afford the cost of "saving more money" by stocking up on electronic components, too!
FWIW, that's what I find most valuable about these types of forums -- exchanging information, expertise and occasionally hardware with fellow hobbyists who've specialized in areas that you haven't.