I created a bedtime calculator called http://sleepyti.me that usually brings in about 10k hits per day. At that rate, I earn between $10 and $20 per day, or $300-$600 per month. Although I consider that revenue to be an astounding success, it is less than half of what you're making right now through the few customers you have.

I agree with cabinguy that a free trial system seems to be your best bet. Don't pull a bait-and-switch with the prices, but offering a 1 month trial that shows how easy and efficient your app is seems like a great way to hook potential customers. Maybe your price point is a little high, and you could be willing to let customers wrestle it down to, say, $200/month. Pricing is difficult, and especially without knowing your niche it's a little hard to say, but the rule of thumb is that if people say it's too expensive, it probably is.

Alternatively, you could meet somewhere halfway and offer a six month "special price" at $100/month or something to see if you can hook people in that way. Either way, I wish you the best of luck!

If you are going to use an ad network (adsense, etc.) you will make almost nothing. Way, way, way less than the $1,200 you are currently bringing in.

Here is what I would recommend: Offer your potential clients a free trial. Let's say 30-90 days. If your product is valuable to them, you will be able to convert them to paying customers. (Like your neighborhood crack dealer. Give it away for free, get them addicted and see who comes back for more! Its a proven strategy.) The key is to get them using your product.

Also, there is no rule stating that you cannot show display ads/text ads AND charge for your product. The only people who complain about ads are hipster/early adopters. If your customers are not redditor types, you can most likely have your cake and eat it, too.

I am currently offering a free, no obligation 1 month trial with no long-term contract. Each customer has their own domain name and I customize each site to match their existing website's look and feel.

I show them testimonials from current customers, examples of how much time can be saved by moving from old systems (usually paper or an Excel spreadsheet) as well as dollar translations from time saved.

Once a customer signs up for the trial and begins using my system, they have already made the decision to keep it for years. The hardest part is having them make the jump, and the price keeps on showing up as the only obstacle. I've tried determining if it is a "fake no" and they have other reasons, but so far that honestly seems to be the only reason.

When you say way, way less, what would you expect for CPM? From reading around, a highly targeted audience (in my case, I know exactly what sort of income bracket, age, etc.) would have higher CPMs, up to $35. If I saw $5 CPMs I would be around $350, so I would need 3.5x the number of customers. I just don't know if $5 is even a number I would be close to reaching with my audience.

$50 a month should be a non-issue for my customers, even non-profit, member-owned ones.

btw, what sucks the most in tennis clubs is finding a court to play. it would be very cool to send a text and say "15:00 today" and receive back a text saying "Ok, booked" or "16:00 is better" or something like that; or "next free slot" and receive back "16:00, court 5. Book?".

We do base our pricing off a few club-size factors, with ~$300 per club being the low end. If they wanted to pass the price off to members, they would see rates rise $0.50 per person per month.