First of all congratulations.

Second, this is a HARD problem, pricing at this level is never easy to figure out.

>But as I mentioned, this is my first app. Had a small corp contact me and they would like me to run an instance of this as a private thing. Essentially either on their servers or (I guess?) from my servers, but from their domain name. It's like an internal around the office tool.

Take a look at this: https://github.com/pricing/plans and then this https://basecamp.com/3/pricing

Both have "enterprise options" that are close in price, but are very different things, and for different reasons.

Githubs enterprise version is effectively a "self hosted white label" --- if you love github and want to use it, but work for an organization like a bank that wants (needs) to have control that 2500 buck option is the ONLY thing that fits the bill.

On the other hand, base camp has three clear tiers... The only reason your going for that enterprise account is because your a LARGE organization, with lots of data or one that needs an SLA (cause your international? or deeply dependent on the product)... white label isn't even an option. This also means that a company might not be able to use basecamp due to compliance/legal issues.

Having looked at these, this request is going to fall into one of three camps.

-- There is a legal reason they want it in house.
-- There is a business reason they want it in house (aka can they use your tool with clients)
-- They are fishing for a discount. 100 people is still a "small" company, can you see them getting $10,000 worth of value out of it?

Some of these answers may be apparent to you, some may not. Do put your sales guy hat on, and ASK QUESTIONS of this potential client

-- Anticipated number of users?
-- Is it a hard requirement that you host this on your own infrastructure (for legal or other reasons)?
-- As well as running this under your own domain, do you need it co-braded, or fully white label?
-- Do you need invoiced billing, is there a preference for annual (with discount) or monthly billing?

With answers to the above in hand you should be able to make an informed guess about what the intent is. Fully white label, needed for clients, legal reasons, are going to be the "enterprise options" that cost lots of money. Your going to end up with a contract that spells EVERYTHING out, including some very high rates for support, and possibly a monthly fee for on call services that are "use it or loose it"

You may figure out that they are looking to SAVE money. If this is the case then its a fairly good deal for you provided you structure the agreement right. A large check today, might mean that you get to move to a reserved, pre paid instance if your using EC2, and you can pass through your s3 costs to them if they pass a certain threshold, bill them for the first terabyte, and tell them that each additional costs 10$ a month rounded UP.

This is also where you have to be careful. If your on a net 30 (you get paid 30 days after you submit an invoice) and then rack up a 20k s3 bill will you be able to cover it out of pocket till you get paid by them? Figure out your fixed costs, figure out your variable costs, break them out, mark them up and pass them along. Bill for everything else is the best option for YOU.

Lastly, Don't be afraid to say NO. Sometimes walking away from a deal is a bargaining chip, but don't take an offer, or offer something up that doesn't make you money.