Your smartwatch can calculate your body temperature and blood saturation levels. The fast-food menu tells you exactly how many calories that cheeseburger will pump into your body. Your weather app knows what the weather will be days in advance.

In this era of instant information, why can’t an SEO company give you a guaranteed price and deadline for landing your business at the top of page one of Google? Famous words: “It depends.” But here’s why there’s truth to that statement.

The most respected SEO firms in the world would undoubtedly tell you that you should be much more alarmed by a company that will give you an exact date for improving your rankings than one that will give you general timeframes instead.

The same goes for cost. While the idea of tiered SEO packages may sound appealing (“We’ll deliver X results for X dollars”), it’s actually a bad idea. It’s like guaranteeing returns on stocks. Impossible and deceptive.

You’re swimming in a vast ocean of variables when it comes to SEO:

Competition In Your Industry

It’s one thing to compete against fat wallets in real estate or finance, or deep pockets of health, nutrition and pharmaceutical companies. It’s quite another to be selling that blue widget that only one other guy sells. More competition = more efforts = more time = more cost for search engine optimization.

Geographical Targets

Are you a pediatrician trying to attract patients in your small town? Or a network of medical clinics with locations throughout the state? Do you offer a product or service in a city vs. state vs. national vs. international? The broader you go, the more competition you’ll have. That will require more effort, more time and more money.

Quality Of Your Website

Beautiful, easy-to-navigate websites with top-quality content will attract more traffic and increase conversions. If your site is weak in page speed, usability or mobile friendliness, you might need a redesign, which will require time and money. Otherwise, you’ll have to decide if you want to “save money” now, but at the expense of delayed growth and fewer long-term returns.

Ever-Changing Algorithms

Even to the most experienced SEO experts, search engines take continued mastery. Consider Google, which changes its algorithms hundreds if not thousands of times per year. These algorithms are carefully designed to keep spammers off their search engine so they can deliver the quality results that keep people coming back to Google for future questions and needs. If they gave away their secrets, they’d lose their competitive edge.

As such, what works today may not work tomorrow. For example, it used to be popular to stuff your website with as many keywords as possible to get the attention of web crawlers. Then, in 2011, Google released the Panda algorithm. It penalized websites for keyword stuffing and turned the ranking hierarchy upside down.

Even Google’s online policies state: “Beware of SEOs that claim to guarantee rankings, allege a ‘special relationship’ with Google, or advertise a ‘priority submit’ to Google. There is no priority submit for Google.”

An SEO company that guarantees results is not accounting for the whims of search engines that can slow or hasten progress without warning. Or they could be using outdated SEO tactics or risky techniques that could do more harm than good. These black-hat techniques may lead to quick gains, but they are not sustainable and could land your site in the long-term penalty box with the next algorithm.

Rankings vs. Conversions

Page One rankings for your golden keywords are often seen as the Holy Grail of SEO, but there’s more to it than that. A company could promise to get you to page one for a variety of low-competition keywords, but this could be a hollow victory if these words aren’t attracting a qualified audience that will buy your product.

A good SEO company will do the research to understand your audience and help you map out the best keywords and content to attract the right buyers. They’ll help you make sure your website loads quickly, is easy to navigate and is trustworthy. All the No. 1 rankings in the world will fall flat if these variables aren’t addressed.

Make sure to ask the right questions when hiring an SEO company so you’re not duped by promises of overnight success. SEO isn’t a cost; it’s an investment. Stop asking how fast or how cheap, and instead ask what the potential return is. The best questions center on how your SEO provider is going to make your site more visible, discoverable, reputable and appealing to your target audience—all while staying in search engines’ good graces.