it is 100% free. you dont have to pay for the game and you can enjoy it for free. if it didnt advertise builders club, then they would go out of buisness.
Even if it's 100% free, you'll be greatly limited to the features, considering the fact that...
-Ten tickets login bonus
1.
-BC is required in order to make groups.
-You cannot make and sell your own clothing (t-shirts, pants, shirts, etc).
-You cannot trade/sell limited items.
-You cannot buy BC-only items.
-You're only limited to one place.
-You cannot join BC-only places.
-You need to pay access to some servers.
-It takes a lot of time to get enough money in order to purchase gears, hats, and clothing affected by the recent price-floors
2 update.
1: Depending on the ticket/robux exchange rate, 10-13 tickets gets you 1 robux. BC gets 15 robux, TBC gets 30 robux, OBC gets 60 robux.
2: The first price-floor was 300 tickets or 25 robux for shirts/pants and 10 robux for t-shirts, but regular users got really pissed off. Since it takes about a month to get that much, ROBLOX changed it to 100 tickets or 10 robux for shirts/pants and 20 tickets or 2 robux for t-shirts.
Yes, you can enjoy the game without any type of BC membership, but you'll miss out on the enhancements.