Searching around, I can find USB testers (some with 3-1 functionality, including USB-C + PD) in the range of $20 - $100 on Amazon and bunch of other websites, that doesn't seem "very very expensive". Would anything be wrong with such devices?

Many of those will just check continuity on pins (which might be enough for what you want) - a full on tester will run actual data at faster and faster speeds until it fails; report error rates, etc.