FIs by no means make much money. But they are making money. At least you have an income and are learning (what I feel is important) good PIC skills. At my old operator, the guys we hired who got FO jobs straight out of school and were from the right seat of other multi crew operators often had better flying skills than the instructors we hired...Initially...
However these guys had no PIC time, and when it came time to upgrade, the former flight instructors outclassed them hands down. You may be able to teach guys straight out of flying school how to be good FOs. But it is difficult to teach someone how to be a PIC and be a good decision maker. That comes with experience and I believe that PIC time accumulated as a flight instructor is extremely beneficial down the line when it comes time to upgrade with the airlines.