Usually if you look after your customers, you get new ones by word of mouth.
You can spend a lot of money and effort trying to attract new customers, when you really should be ensuring that your current customers are getting the best experience, then new customers will find their way to you.
You definitely can't lower your pricing to get ahead, low prices attract the novices who need more help and don't yet realise that help costs money. (I don't mind giving people help, as long as they are paying their way, it's our job, and we love it).
The race to the bottom means you will get less money, more helpdesk tickets and eventually you'll get overwhelmed and that's when the bad reviews can creep in.
We try to sell our services at a reasonable price, so we don't have to overcrowd the server.
This keeps our helpdesk fairly controllable, increasing customer experience and reducing churn.
But one thing to think about. You may have to let your "bad" customers go.
The "bad" customer is the one who always seems to have problems.
Problems like "my site doesn't load on my browser", but it loads on your ie, chrome, firefox, safari and opera, but refuses to flush their browser cache, or pretends they have, when clearly they haven't.
The one who constantly gets their wordpress compromised because they insist on using that 5 year old theme etc.
The one who constantly trips your outgoing spam checking with emails sent from their home, but insists they are not spamming.
Every host has them, you know who they are.
A bad customer can cost you more than you make from them, if they do that they are taking away from your other customers. So think of them as doing your other customers harm, rather than you failing.
Thinking of "bad" customers in this way helps me not worry about dumping them.
Without your bad tennants, your other customers will have a better experience as you answer their tickets faster, have more time to give more precise and explanatory answers. Pruning bad customers may be more effective in the short-term at making your hosting profitable than any SEO or advertising you do.