Taking this overly literally, there's no price to a relationship. Not unless you're actually paying someone to spend time with you. There are ongoing costs, which are more like taxes or maintenance fees, except you're not generally paying anyone for that either. which can be heavily mitigated by a combination of personal compatibility (being with someone who is a good match) and good relationship skills.
Some people demand partners who meet narrow, generally superficial traits or qualities with little regard for compatibility. This type of person nearly always refuses to develop relationship skills, and often has a very poor grasp of how relationships work. In that case, the cost is much higher and may definitely not be worth it.