How to inventory a large collection of LEGO sets
I would recommend taking a look at BrickPicker's BrickFolio feature. It allows you to maintain a list of sets you own, including place of purchase, purchase cost and seal code, and keeps track of the current EBay value on a month-by-month basis. It also tracks CAGR (Compound Annual Growth Rate) - a measure of how well the set's value is performing over time.



Clicking on the set name gives you an overview screen with key set details such as piece count etc.