You're seeing your competition advertising where you can't - or don't want to - afford. You see their banner ads on Facebook, in the "Sponsored Link" area of Google searches, or even on blogs you're reading to relax! Well enjoy that blog read, because guess what: if your website is well SEOed, you may have an edge on them without spending a dime.
Here's why: people are searching for very specific things in search engines. The more specific your content and the more specific you get with it about what you're selling, the better your chances are of attracting new customers. On top of that, the more specific the search, the greater the "ah ha!" moment is for your potential customer, as they found something on your website that answers their need. This is why having good SEO can be more effective than marketing alone.
Marketing can spread your brand image. It can be visual. You can control what your customer sees. With SEO, your potential customer sees a list of search results - boring text. They are hooked by the blue link - your page title - and maybe the black text under that - your meta description tag (or, a random sentence pulled from that web page).
The key for you to get sales from SEO is going to be the clicking experience your customer must do once they click into your website from a search result. You've already naturally hooked them. Instead of them clicking on what they know is an advertisement trying to market to them, they clicked on a search result that feels more organic and natural - like you're not trying to sell something - like you just have the answer.
Once they are on your page, the path to buying what you're selling must be very, very clear. Your goal might be to get them to your Contact Us page, or to a form that produces and instant quote, or to an e-commerce page that sells your product. Whatever it is, the click process to the person getting there must feel natural to them. Your job is to keep providing the answer. Their job will be to follow your breadcrumbs.
If they aren't, if you look at your website stats in Google Analytics (hopefully you use this free services), and you see a lot of one-hit-wonders, aka, people who click the page, and click no further, you've got some brainstorming to do to improve your enticements on your web pages. Get with your website designer and SEO manager and start strategizing.
Master the click-through from search results, though, and you can sit back a bit, and keep that marketing budget on a shoestring!