Brave man for publishing so I am not going to rub it in that I told you so. Far from it you did well to get 100 in and pay £4 for the privilage. Most DJ nights certainly down here are free. Only bands usually command a ticket price.
You would do well to few lessons however and a few tips.
1) Sudents are not the best of customers when it comes to typical spend and with bar takings of only £750 the venue would have made a bigger loss than you. I am surprised that they gave you the deposit back. I would have wanted an absolute min of £1,000 and got it given a typical spend of working customers. My typical take per customer for example was £15 - £20.
2) On-line promotion is great if you can target and you have a great attraction. Personally I have always found from running a big city centre pub that the public are pretty demanding and if the atmosphere in one place on that night isn't rocking they will move on.
Posters all around the town then can pull the crown in and if it is a weekend get them out by Thursday at the latest. BTW. Have a chat with the young guys in all the local offies and give them a free tcket voucher code say £1 quid off for their customers code. We had one young lady worked in THR -----s used to generate around 20 customers every week.
3) Insist - and I do mean insist that the DJ or band do their bit on promotion. I had a great Karaoke act at my place. 2 young girls who claimed that they had a good following. First time they appeared they must have really worked hard at self promotion and brought about 50 people along so I was well pleased with their calim..
3 months latter it was an average of 10. Solution I cancelled the weekly booking and got another act in alteranate weeks. Both teams then made damned sure they pushed all their friends for support up every time they went clubbing.
4) Beit students and particularly girls don't forget incentives to bring friends. Their own ticket free for instance if they bring along 3 or 4 friends. You may lose a few quid but providing your making expenses in the early days the important thing is to get a reputation for making a venue rock.
As LocalBusiness mentioned it is absolutely essential that you work the door.
And finally OP. You and our friend Will P may think different but personally I don't think you will ever make any real money at this because you would need the bar takings as well to make a deent profit on the night. As a paying hobby however it can be great fun.
Be careful of the 40 year + women however if you ever put on a Hen night. Make sure you wear a 'cricket box' then it's only them pinching your bum that you will have to worry about.
R