As you know nothing is truly accurate these days but PriceCharting if you're into web based.
App based (Free) GameEye
My preference is Collectorz which is a combination of Desktop, Web Based and App. It's not free nor do I want it to be because they roll out new features all the time and is by far the most flexible with three different data entry point. It integrated price data from PriceCharting but you can override the PC amount to what you feel is accurate if needed. I have used this now for 8 years and I rather pay the $30-40 a year or whatever it is.