For the most part in the US, landing fees are based on certificated max landing weights. Some airlines have planes with several different MLW to minimize landing fees. But, in EU land, the navigation fees are based on a complicated formula with MTOW only one term, but a major one, so using different weights could save money.
The GLEX has a supplement to use lower MTOW for places like KAPF and KSDL, 75,000 pounds vice 99,500. At SYD, the lower weight implies lower noise, avoiding curfew. Used once!