A few things that can help in detecting scams:
1. Too cheap: If it is too cheap to be true, it is likely not true.
2. No listed contacts: It costs scammers more money to man contacts.
3. Not local: Can you visit the scam store locally? Is it from outside your country?
4. Poorly constructed site: Again, it costs more money to get a better site.
5. whois domain name lookup: contact info, creation and expiration dates, who is the registrar.
6. traceroute: where is your traffic going?
7. Internet user's opinions.
So, let's check out this site
https://www.jhonlinsiteo.com
1. The uke is like 10-25% of the going price; red flag. But the deal seeker is still tempted. Amazon has been known to has price mistakes.
2. No way to reach a person on the site; red flag
3. There's no local stores; red flag
4. The site is not deep; red flag
5. whois shows the site was there just last month and expires next year and shows no contact info (for comparison, whois on amazon says its been around since 1994 and expires 2024, and has detailed contact info). Also, godaddy is used as the registrar (used to be a no-no, but now it is ok). red flag.
6. traceroute shows traffic routed to cloudflare. Just like godaddy of old, anything with free stuff is an invitation. red flag.
7. Internet opinion is this is a scam. red flag.
The key is scammers want to get your money in the cheapest way (before they get shutdown); therefore, they leave a lot of telltale signs.
Based on the results, I don't think this is a Chinese scam (Russian is another country that's bad). This looks very much like a US-based scam (or African as many of them based it in the US).