Welcome to the world of administrative law, nothing is black and white. This is true for a ton of government domains, but tax is the one people interact with most.
Do not be terrified of the hobby vs. business designation. If you take some reasonable, intentional steps, you'll be safe. To be specific: do you segregate the materials for your business separate from your personal property? Do you maintain books for your business? Do you have a separate bank account for your business? Do you regularly operate your business to attempt to make a profit, e.g. selling things for more than you pay for them? If so, it's highly, highly unlikely that the IRS will retroactively characterize your business as a hobby. If you're really worried, get an accountant or tax lawyer to review your practices and give you an "opinion letter" stating that you're operating it as a business. If the IRS ever audits you, you can submit this to show that you were acting in good faith.
Also, what you wrote implies that you might not be aware of this, but you can deduct all of the costs of operating your business vs. your profits, even if it's just a "hobby". The only difference tax-wise between a business and a hobby at this scale is that you can't deduct hobby expenses that exceed hobby revenue, e.g. a hobby can't generate tax losses, while a business can. If you think you'd be stuck paying taxes on the entire profits of your business without deducting your cost of goods sold and expenses, you've been poorly advised.