When we did Complete Works this summer - you were to estimate your house and pay 10% of that to the licensing company and then you sent an accounting of your box office and paid the difference - they recommended you estimate low.  This is the way they did all of their plays.  So yes some companies do a box office percentage.
I don't know which house this was through, but some do operate differently, yes. I was referring to musicals, not plays. Many houses handles plays the same way (Samuel French, Dramatic Publishing, Dramatist, etc) in that they charge amateurs a flat fee per performance (usually between $75 and $100). Few of the companies have a different way (the only one that comes to mind is Playscripts.com) in that you pay the flat fee upfront and then submit a signed box office report to them and pay 8% (if that is more than you already paid)

That price did not even include the rental for music if we go with orchestration.
I did not say it did, did I? Orchestra ranges very broad. Almost all musicals from Dramatic Publishing (including Narnia) are a flat $350+$100 deposit. Piano Scores or Accompaniment CD's tend to be about $250+$100 deposit.

MTI seems about the same as well, generally between $900 and $1,200 (at least from the quotes I have received for up to 3 weeks). Samuel French wanted $800 to rent scores for "The Secret Garden".

For the "big" two musical publishers (MTI, R&H), R&H tends to have the lowest royalties and rental fees. Evita from R&H (with the same ticket and seating) was about 10% with a rental of $400.

If you add in the cost of the Orchextra or Instrumentalease, that runs about $400 a week with a minimum of 4 weeks.

I think it is important for anyone to get a quote based on their particular circumstance and not rely on a formula as you can see I have paid from 10% to almost 20% so it is a wide range depending on the play and the script company.
YES. No single person can tell you exactly what the cost will be. I have never been quoted anything near 20% though. Hell, Les Miserables was only quoted at 14%, and that is probably one of the best selling shows.. If you'll notice in my original post, I stated that the only way to get a sure number is to request a quote. The figured and formula I gave were to get a very rough estimate. IN 95% of the cases, the formula I have will give you a fairly good ballpark figure for most any licensing house. Sure, there are some exceptions, but most of the time that formula will work.

At least, it was pretty close to what you were quoted? In fact, VERY close. So how can you turn around and say that my formula would have put you at 19% Royalty? No it would no. If your paying $145 per performance (after the first performance if $345 - which is new to me. No other licensing house I have received a quote from has charged more for the first performance). $145 of $1,000 is 14.5%, if it not? Is that not what I said could be on the high end?

$145 of $1,000 is not 19%, no matter which way you toss the coin.

PS) This is just my opinion, but I really think you should raise your ticket prices a little more. Most community theaters I can find charge at least $16 for adults. Only a select few I have ran across are lower than this. I understand your desire to be open to more people - but in some cases, people actually perceive a higher price to be a higher quality production (rather it is true or not). I'm not saying jack it up to a huge amount, but I really think your under pricing your shows at $12/$8. NOW, before you go asking me were I have the experience to make this advice - It is not mine. I took that directly from the book "Presenting Performances" by Thomas Wolf, which is a very helpful guide is setting prices, finding sponsors, etc.

We are doing $20/$15/$12 for Narnia and we already have people bugging us to buy tickets (they don't go on sale at the BCT box office until the 27th).