So now you need new ink and are concerned for your budget and especially the environment. You know (or at least you will after reading this) that every laser printer cartridge requires about 3 quarts of oil and 2.5 pounds of plastic to make, and the plastic is industrial grade taking about 1,000 years to decompose!! If you don't consider the option of recycling you are now adding cartridges to the tons of e-waste we already produce.
By now you are probably ready for options. The first is to reduce. Proofread and make sure that once you hit print, you are content with your product to avoid reprinting the same document. Secondly you can recycle your old ink cartridges. By doing this stores like Staples will give you money back which you can use toward your new purchase. Another is to buy remanufactured ink cartridges, which prevent them from landing in a landfill and can sometimes end up being 15% - 50% cheaper and have more ink in them since they are usually refilled up to capacity a luxury you don't usually get with new ones. This option provides you with savings to your budget and the environment without sacrificing convenience.