Manually checking marketplaces for a specific book is the least efficient way to buy comics. You only see listings that existed before you looked and haven't sold yet. For anything in demand, that's the leftover pile. There's a better mental model.
THE PROBLEM WITH BROWSING
Browsing is reactive. You check a marketplace, see what's available, evaluate it, and decide. The listings you're evaluating are ones that haven't sold — which means either they're priced too high, or the competition already bought the good ones.
On a competitive book — say, Amazing Spider-Man #300 in 9.2 at a fair price — a listing can be gone within an hour of posting. If you're checking once a week, you're seeing the books nobody else wanted at those prices.
DEFINE YOUR CRITERIA BEFORE YOU LOOK
The hunting approach starts with a written specification: exactly which issue, the minimum grade you'll accept, and the maximum price you'll pay. Not "I'll know a good deal when I see one." That mindset leads to either overpaying on impulse or passing on a fair deal because you weren't sure.
Your criteria should be specific enough that you could describe them to someone else and they could evaluate a listing on your behalf. If they're too vague to delegate, they're too vague to act on quickly when you're looking at a real listing.
ALERTS CHANGE THE MATH
A price alert with defined criteria flips the browsing problem: instead of you going to listings, the listing comes to you. The key advantage isn't convenience — it's timing. When a seller lists a book matching your criteria, you're notified within minutes, not at the next time you happen to check.
You're not competing with everyone who happened to check at the right time. You're notified at the same moment as every other watcher for that book — and you're acting from pre-set criteria rather than improvising.
PRICE DISCIPLINE BEFORE THE LISTING EXISTS
The other benefit of pre-set criteria: it prevents impulse overpaying. When you set a max price before you're looking at a specific listing, you make the decision without the emotional pull of "this is close enough, I've been looking for months." Pre-committed criteria hold because you made the call cold, from data, not from wanting a specific book to be the right deal.
Set your max from grade-matched comparable sales, not from what you hope to resell for. The market doesn't care what you paid.