It truly depends what you are looking for. If you are purely seeking knowledge, I believe you can get this at a non top-tier school (even taking finance courses part time at a local community college could be beneficial). However, this doesn't give you the pedigree that a top school would provide. It also won't provide the same network or access to recruiters/job placement.

Stanford is arguably the most difficult business school to get in to, but, if you are in the bay area you could look at Haas (still very difficult and considered "top tier" but slightly more realistic than Stanford). Stanford has a great program for entrepreneurs (as does Booth but I'm biased as that is my alma mater).

Most people that go to business school are primarily looking at how much "better" of a job he/she will get after school and use this to calculate an ROI (and think in terms of salary and life long earning potential). If these are your parameters, I tend to agree that your ROI is much higher at a top-tier school (perhaps top 15, not top 10). But, this is a simplistic way to look at what you "gain" from business school. I would never say that education is a waste of time/money/energy (but, given my personal situation, I wouldn't have given up my job and taken out loans to go to a non top-ten school).

I know that isn't the most helpful response, but, without knowing your exact situation and your personal desires, it is the best advice I can give!