WHMCS Expensive

I think you can draw more customers with WHMCS. So because of that your business will be more successful I think. I had tried free billing systems in the past, but when I changed to WHMCS my customers were happier.
WHMCS is a little on the pricy side I agree, but there are alternatives which are more affordable:

Those licenses are nulled you need to check backdoor, I recently met the WebPros team in Bangkok they are building an Echo System in the Hosting industry from ControlPanel to Server Monitoring and who knows they will provide you support service as well.

We are getting Blesta customised for our solution because WHMCS cost is high
If you get enough clients then license fees is not issue. But if you are thinking of $19 monthly costly then surely hosting business is not for you. There are lot many more are required like control panel, security packs, backup softwires, hardware, management etc.
Laslty transfer the costs over to your clients reasonably, again If you want to soften that blow add some extra value, extra space or whatever.

Everything goes up in price, bread, milk instalments it shouldn't be a shocker for them. Some will leave, but most wont and ill pay the higher rate making up for those who left.
Exactly. i dread doing the weekly shop as everything going up at alarming rates.
if you offer excellent service and support then you will find customers will pay any reasonable increase..

Just remember, don't just hit them with an increase. inform your clients approx. 14 days before any increase, and explain to them why you have to increase your prices as the more open you are with clients the more they respect you and will stay with you.
Clients respect honesty more than anything. If you are willing to explain what is going on, why you need to do it, and how it will continue their great service, more than likely they will stay and happily pay the increase.

$19 a month is a lot but when you consider you are trying to create a business, its not. $19 for a billing panel that has been proven to be one of the best is a deal. In addition, the vast majority of web hosting clients out there are used to whmcs so having a host with it is another selling point. Having to learn a new billing system, find out how to submit help can deter people. Something to consider.