Every tile on Shuttle was bespoke and had to be carefully hand-glued. Starship depends on heavily uniform tiles that can be robot arm installed, with truly bespoke tiles accounting for a small portion, in ares that are likely to survive well enough to be re-flown. Also, the propellant tanks aren't lost with each flight. That's just a couple of the differences, I think the biggest, but there are many smaller areas that Starship can, if it hasn't yet, dramatically beat Shuttle in refurbishment costs (money, but more importantly, time.)