Pay per click can be very expensive, especially if you're bidding for highly competitive keywords in the1st or 2nd place positions, but it doesn't have to be.
There are plenty of highly searched terms that are relative to your product or offer, you'll just have to do a little research to find them and think like someone searching for your product.
For instance, look at the dog training niche... The broad keyword " Dog Training" was 3.22 per click with a search volume of 110,000. Now look at the long tailed "How to train your dog" with 3600 searches at 0.77 per click. The more you drill down, the cheaper your ad cost and you'll receive more targeted visitors.
The term dog tricks gets 14,800 searches and only 0.44 per click. "How to train Yorkies" only gets 90 searches, but at a cost of only .05 per click. And that pretty much holds true for the rest of the breeds when you really get specific.
Now, granted, you're not getting 10,000 searches per month with those terms, but campaigns made up using those long tailed keywords will again get you more targeted visitors with ad costs that won't break the bank.