Startup Idea: Thrift Store Resell Evaluation App

Startup idea to develop an application that can query online marketplaces like eBay, Amazon, Etsy, etc. to compare prices and evaluate the profitability of reselling items found in thrift stores.

I sell vintage and gently used items on ebay. I would love to have an application that would query ebay and other similar sites and give me an idea if the items I encounter in the store are worth reselling or not. It could even have a feature where I can input the price of the item and it will compare it with the average going value based on the information it found and tell me if it is worth buying to resell or not.

One of the things that takes the longest while thrifting is trying to ask each site (amazon,etsy,ebay,vinted, etc.) how much an item that is similar or the same is worth. This would be a wonderful idea.