First of all, in response to frontrowcentre2-
THANK YOU for a very, very thoughtful and intelligent response. Sorry I haven't been able to write back sooner, I have been involved with a reading that I have been rehearsing 10-6 since the weekend and had two shows today, but now have some time to respond.
First, regarding "unless you are investing"... as ambitious as this may sound I would like to get into Producing and might be caught up in my personal ideas and views of where I stand regarding this show that I want to make them verbal. You are 100% correct that the financial success and failure of this show won't affect me. However, regarding the artistic success, I do believe that if this show does (hypothetically) become another Glory Days or even to use your example Grey Gardens, if it financially fails on Broadway it won't last long enough to 1. be seen by those who would be affected by its "art" or interested in continuing with there own production and 2. it won't be able to get the acclaim of its artistic capabilities. I believe a critical acclaimed longer run Off-Broadway would provide a better artistic outlet for a small show over a short, if not miniscule, run on Bway.
As you said, TOS was playing towards a basically equal audience at the Lyceum as it was Off-Bway. So for the same amount of ticket sales (with a somewhat increase in price, though most TOS audience members probably used the various discount possibilites) the Producers now had the significantly higher theatre rental costs, higher Actor salaries (due to Equity rules), higher and more stagehand/crew costs, advertising/maintenance, etc. If the Producers kept it at the Vineyard, it might have run for longer and spread to a larger audience over time...
You mention the current economy and the theory of putting in less money into a show... which I agree with! However, there is a difference betwen SITPWG and SOML. As people have mentioned here the latter is a 90 minute musical (that is over $1 a minute) with a 2 person cast and a likely minimal set. Sunday, on the other hand, was a LONG two act musical with a wonderful and creative set and a core ensemble cast that made it worth the money. As you also seem to agree, the main Broadway audience are the tourists and I can't see them paying full price (if not ~$60) for a 90 minute musical that they won't relate to or be wowed by (by it's entire theatrical production quality, not just artistic value).
I will conclude that I guess we will wait and see. I honestly wish it all the best (I happen to have been rehearsing and performing the reading next to Story of My Life rehearsals at Chelsea Studios). However, unfortunately, my business mind as well as my artistic aspirations can't see a positive outcome for what could have been if different producing choices were made (i.e. Off-Bway). I am very excited to hear people's thoughts once it starts previews... and hope that if it doesn't succeed, people will realize that it is more due to poor business decisions than the current economy. SOML, Good Luck!
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To Smaxie and Insider2:
Smaxie, when I saw that you posted, I was excited and presumed you would name a show that fell under my criteria. You did; however, I had said in the other thread and thought it was intended here (which I see that it wasn't) that I was referring solely to musicals. Unfortunately, you named all straight plays and as I mentioned before, in my opinion plays have a very different audience/market and theatrical qualifications. So to clarify, I am looking for a musical.
Insider2: They're... Song opened in 1979 which was 30 years ago (which is out of the 25 year limit I asked). Granted it is close, though it also starred Robert Klein (known for his comedy) and Lucie Arnaz (known for her parents

). I think it is a very valid answer and I would put it right on the line... because I think it opened in a significantly different theatrical and economic time (which is why I said recent). So, I still don't think that is answer but VERY close... :P