I have not done this from a Xojo app. But years ago when I needed EAN scans in iOS from another platform, the performance and reliability of the free/low cost solutions available at the time were NOTHING like the scanning I could achieve using a paid scanner SDK. I first used Scandit and later switched to Cognex, both of which scanned much faster, at greater distances, and tolerated poor quality codes much better.
But since that time phone cameras are much higher quality and have faster processors. Plus Apple may have improved their barcode detection algorithms significantly too.
But for barcodes like EAN/UPC (as opposed to say QR which is more or less designed for quick camera scans), I suggest you test your real world conditions against demo programs from Scandit or Cognex. If you always have good quality barcodes with good lighting etc you may not need a paid scanning SDK. But for high volume or poor scan conditions, at least compare the performance against licensed scan SDKs. (Though I have not used those with Xojo either. My apps for clients predate to Xojo support for iOS.)