penny-wise and pound-foolish
to be extremely careful about small amounts of money and not careful enough about larger amounts of money：used especially to describe something that is done to save a small amount of money now but that will cost or waste a large amount of money in the future.
A example is someone who opts for a cheaper, lower-quality product or service to save money upfront, only to end up spending more in the long term due to frequent repairs or replacements. This could apply to anything from buying cheap tools that break easily and need to be replaced often, to choosing a budget airline with numerous hidden fees that end up costing more than a ticket on a more reputable airline.
Ultimately, being penny wise and pound foolish can result in short-term savings but long-term financial losses if important investments or expenses are overlooked or compromised in the process.
