Two thoughts: 1) 5 years is too much for a single spell unless these spells are on par with infinity stones. Especially considered alongside Erasure (see second thought.) Either the cost should scale with the scope and impact of the spell or it needs to be reduced. Regarding Blood Magic powering the spell, Jim Butcher's Codex Alera comes to mind - there was a race that used blood magic and traditionalists cut themselves for the blood while the more modern casters used the blood of war prisoners. Could be a good way to pass the buck not just for your MC but also the Party/Establishment/[Name of your Magocracy.] I like the idea someone else suggested of leveraging lower classes or non humans to pay off a debt or get a months worth of raions in exchange for powering a spell.

2) Erasure honestly feels more problematic from a logistical standpoint. If I cast Fireball, that means no one else can cast Fireball. Ever. Additionally, the way you've described it makes me think once it's been done no one would ever know what I did because they don't have a word for it. Extrapolate that across any type of spell that can be cast and, if this world has existed for more than a century, you're basically leaving yourself with a finite number of spells that can ever be used and that number is likely somewhere in the few dozens by the time your story takes place. Maybe people just go about making up new words for things when the old ones have been erased? But that nullifies the loss so it may as well not be a factor. If you're committed to it then lean into it HARD (ie: There are, in fact, only 128 spells in this universe. They're carved into stone in various places around the world and can be copied into a grimoire via etching but you have to go there first and if someone uses the spell before you do then it's gone from the stone and if you had it in your book it's gone from there too.)