All depends on the specific make / model / source. I have to add that last point in there 'cause you can get bikes labeled 'SSR' or 'SDG' for instance that only share badly copied graphics with the brand they claim to be. There are good units out there that don't quite hit Honda quality but do ok, and there is some true barrel scraping bottom feeding literally made from poorly pressed together soup can crap.
The dealer near me sells the Apollo brand. I'm looking at their 125cc. I thing the website advertised about $750-800. It would be for trail riding with my 8 yr old and possibly do some riding at the Herrin compound. Every 100cc and up I can find is at least $1000 around here and it's at least 10 years old. I know u get what I pay for
Apollos are heavy, and generally the lower end of the market. For casual play time, they are a cheap way to have fun. If you want to seriously race them, consider upping your budget.