Ultimately, selling something always requires a return on investment that makes the entire process worth while. The essential question is whether the cost of raw materials, tools, and your work can yield an income that both covers that investment while generating a worthwhile profit.
I found that it takes me roughly 3 hours to make a nicely finished birch plywood or a stainless steel bent rod slingshot. The investment in terms of raw materials is actually quite low per unit, but it is the quality focused hands-on work that accounts for the the key cost factor, assuming that I were to sell my products (which I don't).
Swiss labor costs would imply that I would need to charge roughly roughly USD 100-120 per unit to allow for a relatively small profit, which is totally unrealistic considering that potential customers can find a nicely made mass produced Chinese slingshot made of 304 stainless steel and quality wood for approximately 25 to 30 USD, or alternatively, an injection-molded plastic slingshot for roughly the same price made in the US.
Clearly, unique slingshot designs with significant artistic input and original styling will command far higher prices as collectibles, regardless whether they are made in China or in the US. It's like Rolex vs. Swatch, speaking from a Swiss perspective.
Thus, the key issue is to bring down unit production costs to a level that enables you to sell your slingshots for a price consumers are willing to pay, particularly during times of severe economic hardship (by courtesy of the CCP-Virus), while making your investment in terms of raw materials and workmanship worth while. If mass production based on automated machines is a possibility for you, then go for it. Otherwise, you may be better off just making slingshots for yourself, family members, and friends.
Last but not least, your slingshots need to stand out in some way to be ahead of the significant competition already out there: you will need an original design and will have to test the market with what you come up with. I am not trying to discourage you, but all these factors do need to be taken into account,
My 2 cents worth...