It's a good idea actually, not only to know where you stand, but more importantly to gauge progress.
P.S. OP not directed towards you, but this is sdn pre-med crappy mentality to save every buck and live on a ramen. If someone thinks nbme isn't worth $50 given that they literally pay hundreds of thousands for their education - then he/she is an idiot (from latin - person who has no clue, so I'm not offending anyone lol). You are not a fastfood worker who can lick their snots or wipe them with their shirt, you are a future doctor and actually need to invest in yourself be it nbme, healthy food or a goddamn handkerchief to wipe your nose properly. Pre-med life has ended.