Is there any better AR tracker than the AR starter kit gives us or it would be much better if we can track without the marker
You can use https://www.8thwall.com/ with PlayCanvas which has a large range of AR options and features.
aren’t there any options that are free or cheaper?
WebXR API is still in draft stage so not suitable for production yet.
You can try ar.js but there’s no PlayCanvas port/integration: AR.js Documentation