With that stated, generally, I'd say close the beta application process and let in the first x number of applications you got. Send each application a thank you note and tell them that you'll let them know once you've moved out of beta. You may piss off a few people here, but 100% of zero is still zero, so you're better off with the money.

That's my take, but again, background information would be nice.

It happens.

You have our attention now, though, so you should try it again.

I don't think anyone will deny you the right to make a living based on the fact that you said something overly specific in the past.

It's really hard for us to judge what kind of buy-in, etc. you'll have without knowing what you're offering. For porn it's 0,1% or less - for Rolls Royce engines it's 50%.

I would use the momentum you have and compose a mail telling your beta applicants, and potential customers, that everything is going much better than you could ever hope to excpect, and that you're happy that you can solve so many problems for so many people yada yada, and that you don't have space for more betatesters but will soon be offfering the real deal, and will send them an e-mail when this happens. And don't wait too long, they'll have forgotten about it in a month.

also, many will sign in once or twice and never come back. not all beta members will be active members.

Be open & honest with those you turn down. until you can invite them, keep them in the loop with a periodic newsletter. maybe even poll them if you need customer input.

If it's a monthly service, I'd say offer a 30 day free trial (if you don't already) and possibly a small ongoing discount.

Because the question is how do I increase paying users and the (unstated constraint) growth is increasing which costs. At some time the service has to become ramen profitable.

Good point.

Do you think it would it deter users if they wanted extra features? Casual users might want to stick with zero cost but I wonder if business users might be willing to be charged for extra features that free users cannot use?