Depends on the state of the building and when they sold. Some people are forced to sell if a special assessment comes up that they can't afford and then the assememt price is usually factored into the sale price (which may explain the price discrepancies you describe)
Probably worth it to get a good inspector through and investigate the work done. Especially the envelope. What is the age of the building, why was the plumbing replaced? Etc
Btw, I can appreciate the hesitation in hiring an inspector because there are a lot of hacks out there, I'm currently training to become a certified home inspector with 15 years of construction experience so there might be a revscene discount down the road for anyone interested
