The Paris Métro system is extensive and often more cost-effective than taxis or rideshares. Consider purchasing a Paris Visite pass for unlimited travel on buses, trams, and the Métro for a set number of days.
While areas like the Marais or Saint-Germain are popular and centrally located, you can save on accommodation by staying in less touristy areas like Belleville or the 13th arrondissement and still easily access main attractions via public transport.
Avoid restaurants in tourist-heavy areas. Instead, opt for local bistros or purchase fresh produce from local markets and have a picnic in one of Paris's many parks. Also, look for restaurants that offer a "formule" or a set menu for lunch — they're usually more affordable.
Many of Paris's attractions, like the Notre Dame Cathedral (pre-fire) or the Sacré-Cœur Basilica, are free. Also, Paris often hosts free events, especially in summer, such as outdoor film screenings and concerts
Paris's tap water is safe to drink and is of high quality. Instead of constantly buying bottled water, carry a refillable bottle and save money while being environmentally friendly.
Attractions like the Eiffel Tower are undeniably iconic, but the surrounding areas are often marked up in price. After you visit, head to a less touristy area for meals or shopping.