I don't mean $1/month as a cheap promo, I'm referring to a situation were the costs of running your SaaS is very low, were you can break even with a few hundred

I don't mean $1/month as a cheap promo, I'm referring to a situation were the costs of running your SaaS is very low, were you can break even with a few hundred customers a month. And adding new customers doesn't significantly increase your cost. In this case you can afford to charge $1/month and take advantage of the volume. You can provide limited support for basic accounts and charge much more for full support like $5-$9/month. The idea is to give your customers the only-pay-for-what-you-need model which is very realistic on the web. If your cost increases significantly with each new customer you acquire then find what will increase your costs and charge extra for it, maybe bandwidth, computation, disk space etc.