Is staying off site of a convention cheaper then staying at it?
The answer I've found after researching it a bit and talking to many people about it is usually - no its not.
Here are some things to consider when trying to decide if you should go with the more pricey room in the hotel the con is happening in or right next to or if you should go with the cheaper one a bit down the street.
A lot of time people will book the hotel down the street as a means of saving money without thinking about the things that staying farther away from a con add's into the mix. The factors listed above are some things to consider when deciding and here's why.
Parking - A lot of hotels (specially in cities like NY, Baltimore, Boston, etc) will expect you to pay extra to park in their lot or garage because of how little space is available on the streets and also the extra security they can provide to your vehicle. What many people don't realize is that often times if a convention is happening inside a hotel they will offer free or discounted parking for people attending the convention that weekend. Instead the book the cheaper hotel and pay to park, which while by itself doesn't usually end up equaling the same cost of staying at the pricey hotel when added with the next factor it can.
Distance - If your hotel is a half mile or more away from the con chances are you won't be walking to it, specially if it is happening in the middle of july or february and you're in costume. This will lead either to the expense of driving to and from the con daily (and in some cases parking) or to the expense of taking a taxi or other transport to the con. In this case the amount of money you will have spent driving back and forth (and parking) or getting taxi's (sometimes mulitple times for both) will equal out to be the same as having stayed at the con. You also have to think about if you are walking and want to leave the con for a bit how you are going to feel about needing to walk back later. As well as the time it will take to do so.
Time - Staying away from a con cuts into your time. The time you have for sleeping, eatting, getting ready, attending the con, etc. No matter if you are driving or walking you will need to figure that you will be missing out on something you wanted to do at the con at some point simply because it is taking you longer then the people staying at the hotel the con is in to get there. For them they have a 2 min walk or elevator ride down stairs. For you it will be a 10 - 30 min ordeal depending on distance and traffic. In some cases you might realize that with the time you spend traveling back and forth equals out to missing almost a whole day of the con at which point you have to ask why you paid for a 3 day pass when you really only spent about 2 days there.
Food - You will almost always end up leaving a convention to get food but there is a difference in this subject matter for those staying away and at the con. If you are staying away any food you bring with you will be left back in the room because you wont want to carry it with you, this means going back to the room to eat or in most cases as this is how people who leave the con to eat thing you will go out to eat at a restaurant. Again cutting into the time you are at the con and adding to the expense of traveling back and forth if you are not within walking distance. For those who stay at the con they simply can go back up to the room, grab something, and be back down in the con within 8 mins. Missing nothing important and getting head starts on lines. They can even order a pizza to there room and go sit in the middle of the con and eat it without ever having to leave the fray.
One final thing to consider that is not listed above because it is not a cost that will effect everyone in the party is:
Roommates - If you are rooming and traveling with multiple people and are staying away from the con and it is not within walking distance one or more people are going to end up paying for a ride back to the hotel. Not everyone will want to leave the con at the same time and usually the driver of the car gets the say as to when they are leaving. If they want to leave at 8 pm and you want to stay till 1 am you will be faced with paying for a taxi or bus by your self. Even if you are within walking distance you may find you are the only one who wants to stay late and be faced with walking back to your hotel, alone, in a strange city, in the middle of the night. While this may be fine for a few tough guys out there, if you are a girl dressed up as sailor moon it may not be the best or safest choice and you may find your self leaving the con well before you are ready to simply for your safety.
Again these are just some things to take into consideration when looking into staying at a con verses away from it and every situation is different. Some cons like NYCC are just so pricey that staying away with all these factors is still cheaper and others like metrocon can swing either way.
The fact is you should always sit down with those you are traveling with and have a serious talk about how late people plan on staying, how often travel back and forth to hotel and con will happen, and price out these extra added costs to determine which plan is truly better for you.
A great place to inquire about this and get feedback from others is in the forums of the actual cons and of course at cosplay.com