You have one site and one problem. Either you need your link on the most relevant page that already ranks, or you need links that do not exist yet. Those are not the same job.
Look at a link you already paid for. Open the host page in any SEO tool. Does it actually pull traffic, and is it about your topic? If the page has standing and matches, the link works. If not, you bought a number, not a result. That check is the decision this page is about.
Not a new post built to host your link. Not a page that has to earn its own traffic first. An article that already pulls traffic today, on a page Google already trusts, where your link sits in a sentence that was going to be there anyway.
Picture a guide that already ranks on page one for your core term and pulls steady traffic. Your link sits in a sentence about exactly that term, so it inherits the standing and the relevance that page already earned. A link on a page nobody visits and nothing ranks for passes almost nothing. Most link work optimizes for the first and approximates the second. We start from a page where both are already true, and you can see both before anything is placed.
Link Building creates links that did not exist before. You reach for it when what you need is reach the index does not yet hold, not a placement on a page already ranking. It is its own path, with its own scope. We do not blend the two, and we do not price them as one, because they are not the same work.
Priced per placement. Link Insert and Link Building scoped and quoted separately.