Bad Dog 505

So I've got a 2013 chu613 Mack rawhide with an Eaton 18 speed mp8 505 horse motor long story short, as of today in the three years I've owned the truck, after getting about two and a half years of actual usage out of it, due to the fact that it was parked from December to August of 2018 because I couldn't afford to pay for the repairs on it and was already in debt to the company I work for, for $15,000 does $30,000 in exhaust aftertreatment expenses in 3 years sound excessive?