You would report $10 of hobby income.
You are allowed to subtract the "cost of goods sold", but not other expenses. From Publication 535:
You can determine gross income from any not-for-profit activity by subtracting the cost of goods sold from your gross receipts. However, if you determine gross income by subtracting cost of goods sold from gross receipts, you must do so consistently, and in a manner that follows generally accepted methods of accounting.
https://www.irs.gov/publications/p535#en_US_2020_publink10004353
https://www.law.cornell.edu/cfr/text/26/1.183-1#e
