This sentence could be interpreted as funny due to its usage of dark humor. Dark humor is a comedic approach that mainly capitalizes on subjects that are generally viewed as distressing, serious or taboo. In this case, the statement compares the cost of an abortion procedure with the "free" alternative of falling down the stairs, which is a harmful and dangerous method that can induce miscarriage but can also be risky for the woman's health or even life. The humor lies in this shocking, unexpected comparison which joltingly deviates from the usual advice on frugality one would anticipate.
Secondly, the irony in this sentence lies in its socially inappropriate and crass nature. The statement seems to be presented as an advice column or a tip, a context that usually conveys helpful and practical knowledge. However, the tip given here is extremely dangerous and unethical, making it ironic that it's presented as a sound piece of advice.
Thirdly, the sentence juxtaposes the serious matters of health and safety with the trivial pursuit of saving money which introduces further irony. It trivializes an extremely grave and personal decision such as an abortion by reducing it to a mere financial transaction. The implication that personal safety might be put at risk to save money thus generates a discordant image which may seem absurd or funny to some.
Moreover, the phrase "I'll be back next week with more money saving tips" increases the humor and irony of the situation. As such serious decisions become equated with thrifty shopping on this absurd "advice" channel, it builds up the sense of anticipation towards what other ludicrous "money-saving" advice could come next. This absurd dose of anticipation enhances the humor in the sentence.
Moreover, the sentence taps into the element of surprise in comedy. The majority of humor revolves around unexpected outcomes, twists or turns. In this instance, the sudden shift from the sober topic of abortion to a whimsical money-saving "tip" serves as a surprise punchline, adding an extra layer of humor to the whole situation.
Lastly, the humor in this statement may depend on the demographic of the audience. To some, the sentence may not be funny at all due to its insensitivity towards a highly personal and emotional decision. However, for those who appreciate dark humor and the blatant disregard for political correctness, this sentence may elicit laughter. Essentially, the humor and irony in this sentence can vary greatly based on individual taste and comedic preference. Paying for her abortion makes no sense when stairs are free I ll be back next week with more money saving tips