Kylie Jenners 18th Birthday was a big business for her and everyone involved.

Kylie Jenner's 18th birthday party in Montreal was big business for everyone involved ... not only did Kylie make big money, but the club AND the promoters scored six-figure paychecks. 

According to our sources, Beachclub raked in $150,000 for KJ's big day, while the promoters took home around $100,000 (they took in $300k at the door, but paid Kylie $200k to show up).

Beachclub's owner, Olivier Primeau, tells TMZ he spent an additional $30,000 just to make sure the night went flawlessly. Here's where some of that extra money went:

-- $1,500 to build a deck so she wouldn't have to walk in the sand in her heels.

-- $4,000 for 2 specially built private bathrooms near the stage, so Kylie wouldn't have to go thumping through the crowd to use the restroom. 

-- $10,000 for security, which included 100 security guards.

hmmmmm. This babe dey pull weight sha!!