Ratings are only useful for comparing relative player strengths, and then only represent a statistical view of the difference in strengths. The system used on chess.com is very similar to the USCF and FIDE ratings, in which ~2300 is the beginning of "Master" strength, ~2600 roughly equates to Grandmaster, and ~2800 gets into the world champion candidate levels. Various organization's systems might be 100-200 points higher or lower depending on the population of players. The chess.com ones seem to be inflated a bit vs. the traditional ones.
In the FIDE / USCF / chess.com system, a rating of 9000 would indicate the player is something like 25 standard deviations from the center of the rating curve, and would statistically be only losing something like one game in a million.