The costs get kind of complicated since various bits get out of date and have different value. For example, there is speculation that a finless "Starship" that

The costs get kind of complicated since various bits get out of date and have different value. For example, there is speculation that a finless "Starship" that had been seen at the site some time ago which now appears to be being scrapped without any use was thrown together in case S25 was not ready in time for the second flight. So while construction wise they spent money, is that money that was part of the test cost? Similarly, they're moving to Starship V2 and Raptors are moving to V3, making the previous hardware obsolete. But since they can still gather data from launching the older hardware, they will launch and lose it since scrapping is supposed to happen anyway. So at that point losing the vehicle in flight hasn't cost them much more than just scrapping it. However, since you probably mean actual construction cost, the boosters must clearly be expensive, thus their interest in getting those working even if it means sticking sacrificial Starships on top. I'd guess each unit is probably around $40-50 million each. Still revolutionarily cheap per kg, but certainly not so cheap that they can keep endlessly throwing them away on incremental steps.