Just wanted to clear things up in regards to why carts sell instead of eliquid. The main reason is because 90% thc is the strongest and cleanest not having added any PG/VG or other cutting agent but this thick oil wouldn't work with your everyday atomizer that uses cotton coil. There are cutting agents available ready to mix with any concentrate and to fill in your normal vape mod but most of these liquidizers contain not only PG but usually a mix of PEG400, 600 etc which is not well accepted in the canabis community as a healthy cutting agent with your medicine. Therefore people choose the most organic way which straight thc distillate and a small amount of organic terpenes that is widely accepted for it being natural and the best alternative for cutting your concentrate to make it vape-able in the appropriate atomizer cartridge.
Hope that helps :)