Ehn, 50 bucks without transit?
The problem becomes size. If we're talking anything larger than holding it in someone's house, the costs listed skyrocket.
If you're renting a venue and equipment, you need security. You also need to discuss overnight or after-hours rates, because the vast majority of venues do not have experience with LAN parties. Because we're mostly old fuzzy bunnies here, we probably won't be pulling 24-hour shifts, but if the last couple LANs I've been to are any indication, we're going to want access until at least 2am. Most venues don't do that. At the same time, if you want this to be a repeat thing, you need to broach the topic of power consumption. Again, almost nowhere is ready for the sheer draw that X number of gaming PCs is going to have. You don't want to get slapped with a bill for it after the fact. Even if we stop at midnight to hit the bars, power consumption can go to thousands of dollars in that time.
There are basically no large LAN parties smaller in size than Dreamhack, Quakecon et al because the sheer weight of these costs require numbers to defray them. Personally, I have run one and the general consensus was "not worth, would not do again." (in monetary expenditure)
If you're going to do this, look up veteran association halls. They are medium-sized, generally extremely flexible, willing to work with you, and badly in need of money. Consider a BYOC policy and have a waiver ready, regardless of your security arrangement. You're going to need infrastructure, but Home Depot will pretty much have anything you need for rent, and for cheaper than a party place (tables, srs-bzns power extentions, I usually make people bring their own power bar and recommend a heavy duty one). If you're going to want this to be recurring thing, you're probably gonna want to invest in the digital infrastructure yourself, which means a switch and router at the very least. You can ask people to bring their own cabling, just make sure they understand the length they need, which should more than the length of your hall to allow for play. If you're doing it yourself, buy in bulk from like (GODDAMMIT I FORGOT THE NAME OF THE PLACE AGAIN). Relatedly, you're gonna need a fuzzing shitton of gaffer tape to keep the cabling safe.
Basically, what I'm saying is I've done this before and while it can be done it is not cheap and hard work. There's a reason all our LANs these days are small and at people's houses.