You arent missing anything crazy on the official app, eBay just hides those completed filters deep in the menu sometimes. Try using a desktop browser on your phone if the app keeps acting up, just toggle desktop site in your browser settings and the filter on the left sidebar will actually load properly. Make sure to double check that you are looking at sold items and not just completed ones, since green prices mean it actually sold while red just means the listing ended. Also Ive been using Price Drop Catch for a few months, its free and doesnt need an account which is the main reason I stuck with it. Be careful pricing older stuff like comics too, condition is everything and sold comps vary wildly. Let me know if you need help finding the filter!

Desktop mode is the safest bet here. Just open your mobile browser, request the desktop site, and check the sold items box in the sidebar filters.

Building on the earlier suggestion, I would suggest being a bit careful with mobile browser workarounds since eBay constantly tweaks their responsive layout to break desktop view on phones. Since you are just trying to price a few comic books on a tight budget, make sure to watch out for these data points:

• Raw listing titles can skew results, always check if the comic was actually graded by CGC or CBCS.
• Filter strictly by "Sold" and not just "Completed" green means actual cash changed hands.
• Keep an eye on shipping costs because a cheap comic with twenty bucks shipping ruins the data. I hope this helps you get accurate values without spending a dime on subscriptions. Let me know if you need help decoding any specific comic grades!