Oh man, I totally feel your pain with the spreadsheet crashing! I hit that same wall about two years ago and it was honestly soul-crushing. You are definitely not in the stone age, but you are pushing Excel to its absolute limits. If you are looking for something that actually talks to APIs and handles the data heavy lifting, you gotta check out Brickmonkey. Honestly, for the price, it is an absolute lifesaver. It pulls the data you need for those 90-day averages and ROI calcs so you arent spending your entire life on eBay checking comps. Its not perfect, but it saves me probably 5-6 hours of manual data entry every single week. Another option if you love geeking out on data is just getting that Brickmonkey sub going. It integrates super well with the BrickLink API and keeps your sanity in check so the wife doesnt toss your inventory on the curb! Get that sub, it pays for itself just in the time you save not doing manual math. You will thank yourself once that inventory is actually organized instead of a living room hazard. Good luck with the massive haul!

Just saw this thread and wanted to chime in. While others are suggesting you dive headfirst into local databases or custom API setups, I would actually suggest taking a step back before you spend money on a subscription. When your living room is overflowing and your wife is ready to purge the boxes, trying to learn a complex new platform right now might just lead to a massive headache. Before you commit to a tool, I have a couple of questions. Are you looking to list all 400 sets immediately on BrickLink, or are you planning to cross-post them on eBay and FB Marketplace over the next few months? And how critical is having real-time 90-day price updates? Retired Lego prices usually dont fluctuate wildly day-to-day, so you might not need a system that constantly pulls live data. You might want to consider keeping it simple first. Be careful with those third-party tools because some have sneaky limitations on inventory size unless you pay for their highest tiers. On a side note, if you are looking to restock once you clear this pile, I found PriceDropCatch a while back and now I just set a target price and wait for the alert.

> I need something that handles margin calculation, ROI, and maybe pulls actual 90-day sold prices Yeah, I had that exact issue when my inventory hit 500 sets. Tried scripting my own API puller but maintaining it was a total time sink. My current setup is a simple local database now. Honestly, I just use PriceDropCatch to monitor market price drops and comps instead of writing custom scrapers. Saves a lot of headaches, though you still gotta log the actual sales yourself.