Guys i need your opinion on this issue I've been working in a startup for almost a year now.. the product we are building is pretty awesome.. the only issue is the non technical managers are giving unrealistic deadlines to the clients and we the development team guys are under a lot of stress.. they are not ready to give us a raise as we have not come out beta yet.. should I stay or quit?

I think we need more info. In any case the PM's should have a reasonable schedule and all stakeholders should be aware of dates.
I think you should speak with management and not quit yet. If the product is awesome try every angle before walking away from it.
Thoughts?

If you dont own shares or something, do a good job but chillax. This actually also helps tremendously with doing an even better job.

You're in control. Remind them of that.

if i were you id make an entire schedule of the milestones with the logical delivery dates according to your estimates.
have your fellow coders in on it, approve it, and send to higher management.
if they boast, you gove them a taste of their own medicine: "if marketing gets to decide due dates feasibility, then you shouldnt mind accepting our [the coders] logical timeline"

@Unipheas @Jumpshot44 the issue is we really wanted to show the stakeholders something by this month end so we worked really hard and deployed a alpha build of the app.. they took advantage of this and decided on adding 8 more features which were not meant to be in this sprint

@amjo the milestone for the alpha build was august.. we brought this on ourselves by finishing it by this month end.. now they think we eat lightning for breakfast.. what they don't know is, we only did that to get feedback from the alpha users and tweak the beta version based on their feedback.. the founders and the marketing team have no startup experience they all worked in big corporates they think the users will buy anything you throw at them