brmore
1) If you were going to get equity you would have it already. It would have been a condition of your employment, in writing. Anything else is empty promise, as I fear you are beginning to discover.
2) Even if you HAD equity, that equity is WORTHLESS until the company is sold or goes public. Equity only has value at exit or if the company is going to pay some sort of dividend. From the sound of things, both are unlikely.
3) I know you feel like you are invested in this company, that you deserve better ... and you do. That loyalty that you feel to the company does not appear to be returned. As an employer, that is a massive failure. One of the true perks of being a bootstrapper is that I am empowered to give people the "breaks" that make my place fun to work at and family friendly.
I think that it is time for you to move on. Follow mmaunder's advice carefully, especially the part about not talking about ANYTHING you're planning with co-workers. At best your co-workers may unintentionally break your confidence, and at worst will do so in an attempt to curry favor.
Also concur with petervandijck earler. Might be interesting to just post your company name here. You might find a taker.
As to valuation, I wish there was a magic formula. I know from my own experience that the seemingly harsh valuation of a suitor will NEVER equal the company's value in your heart. Don't allow yourself to be insulted by an offer, at least publicly; you will almost certainly be angry, insulted, and frustrated at the value others will assign to your baby.
Concur with some previous comments that price page needs attention. Sounds cliche, but go back and look at some of the older 37signals.com/svn posts on making purchase process easy/intuitive/good design.
Also, can confirm that page is dorked somewhat in IE8 ... pretty sure it's not the look that you were after! Let me know if you need a screen cap / don't have IE to take a look.
Nice job! You're hard work has paid off, but it AIN'T OVER. Keep the press.