Would this strategy work in the long run?
Maybe.
Lets talk the general first:
@RGB_11 and
@AlvinofDiaspar both correctly note that making up the reduction on volume is one of two core strategies, the other being a hybrid.
I know the industry, and the typical margin on even an elaborate coffee leaves room; but that is, as noted above, dependent on rent, staffing and other costs.
The other core strategy is essentially loss leader (or in this case, low margin leader), which you get someone in your resto/store lured by the lower priced item, and then they pay for a full priced one while they are there.
This is the concept a of discount movie ticket, particularly for children, and then you make it up at the concession stand, its the same as a supermarket selling name brand bacon at $4, but then you buy the bread, the salad pack, the tomatoes, and the mayo for your BLT at full price.
Its also the principle behind $1 pop at McDs in the summer, and $1 coffee in the winter.
Does it work here? Does she sell muffins, and what's the margin on them? (answer below)
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Specific to her place:
She's only 60ft2, renting space inside a laundromat, on a second-tier road. I would hope her rent were quite low.
She's also the only FT staff as I understand it.
That provides a lot of wiggle room, but also limits her hours.
I just checked, and she's 8-4:30 weekdays with a 9/10 start on the weekends.
On food, she's got a small selection of cookies, 'breakfast loaf (think carrot cake slices) and a few other goodies, along with some merch, and she also pushes sandwiches as well.
I think its viable but not without risk.