Just like i expected new players or lower levels are struggling to farm fb blood since not many people are tabbing at their level. Please consider adding another way for them to get blood. Maybe drops from the bosses.
Edit: As a raw ideea if you would implement boss drops, prices could be increased at the exchange npc to make it relevant and it would create some diversity in things to grind too. Also if some people are worried that higher lvl players could "abuse" low lvl fbs, you would mostly farm training esoterica, rep and later on tome fragments and pages and i dont think thats game breaking, with the proper balance. The basic ideea here is to help new players get started easier