Eighteen dollars for a single tube and unknown brand? That's crazy. I've used several different brands and never saw a difference between them. That includes Sunlite (China or Taiwan), Kenda (Taiwan). Conti (Germany), and a few others I don't see online right now. Last time I bought a package of 5 Conti 700C X 23 tubes they were $5 each with shipping from England. Price is now $9 for a single tube with free shipping
https://www.ebay.com/itm/115159970079 and a US seller. The Sunlites are even cheaper at $6
https://www.ebay.com/itm/381934153635. I stay away from Schwalbe because all of the "reasonably" priced (cost + shipping) sources are overseas like this one for $13
https://www.ebay.com/itm/284875966404. If you need them fast, use a US seller. I've used Schwalbe tires and tubes. IMHO nothing special about them except for the cost.