I’m going to answer each question best I can and then if someone finds an issue with it, I’d be happy if they added more color/corrected me.
1. Yugo K98s are captured German K98Ks that were refurbished in Yugo arsenals. Example: If a barrel was shot out, they’d manufacture a new one and replace it. If a stock was broken, they’d replace it. All waffenamts and German markings were scrubbed except for Mod 98 designation. They’d restamp the rifle with their markings and if everything was good for service, they’d force match parts and give it a new serial number. So, technically yes you can get one Yugo numbers matching.
2. I don’t own a Yugo K98, never even handled one. Given the above information I’d assume most are matching, but you know what they say about assuming.
3. After WWII, Yugoslavia wanted to rearm the military for potential future conflicts and capturing K98Ks was an affordable way to do so. A lot of these rifles were left behind in Yugoslavia and capture by partisans.
4. Few years back a good price was probably $400-$600 depending on condition, but now who knows. People are paying $1,000+ for Russian captures, so if I had to guess, people are probably selling them for $800.