Answer:
A lot of players are Professionals in the sense that they play the game for the purpose of earning an income, however, earning your entire living off nothing but blackjack is next to impossible for a number of logistical reasons, though in theory it is possible, and I woudlnt doubt there are a few people that do it especially in the realm of team play.
Professional blackjack players will most likely enter the arena as card counters, depending on a card counters betting approach toward attackign the game, they will hold an edge over it upto about 1.5% or more if the game is extremely vulnerable.
This means that on average, every 100 dollars put into action is worth $1.50 to the player. It then becomes a battle of how many hands you can play at an advantage, and how much money you can put on them. Though for most 8 deck games, the player can expect around 20$/hr placing 100 dollar bets, $40/hr if they play 200/hnd, and even more if they play 2+ hands simultaniously.
The limit to how much you can make will come down to one of several limiting factors
-Hands are dealt at a rate of 60-300 hnd per hour depending on the number of players at the table.
-A card counter will only place bets (or expect to win money) on about 15-25% of all hands dealt and observed
-A player cannot bet over the posted table maximum. which is *typically* 500 1000 or 2000 depending on the casino.
-Players betting large amount of money in contrast to other players at a table will stand out and become the focus of scruitiny which may lead to a backoff from the table. Typically, anything over 150-250/hnd consitantly will raise eyebrows but this depends on the casino.
-You cannot play the same casino in front of the same employees for 8 hours a day 5 days a week, and not be detected as a card counter in a short time frame.
All in all $15,000 to $40,000+/yr is not unreasonable if you can play the game a lot. Certainly not enough money to retire off of.