Is the word custam the same in Brazilian and European Portuguese?

No.

While the spelling and fundamental meaning of "custam" (the third-person plural present indicative of the verb custar) are identical in both dialects, there is a difference in typical usage regarding syntax. In Brazilian Portuguese, it is natural and common to place the object pronoun before the verb (proclisis), whereas in Continental Portuguese, the pronoun is typically placed after the verb (enclisis). Additionally, there are slight differences in pronunciation, specifically in the intensity of nasalization and the articulation of vowels.

Brazilian Portuguese Examples

1. Esses livros custam cinquenta reais. (These books cost fifty reais.)
2. Essas matérias me custam muito. (These subjects are very hard for me.)
3. As passagens custam muito hoje em dia. (Tickets cost a lot nowadays.)
4. As lições custam a ser entendidas. (The lessons are hard to be understood.)
5. Esses cursos custam uma fortuna. (These courses cost a fortune.)

Continental Portuguese Examples

1. Estes livros custam cinquenta euros. (These books cost fifty euros.)
2. Estas matérias custam-me muito. (These subjects are very hard for me.)
3. Os bilhetes custam muito hoje em dia. (Tickets cost a lot nowadays.)
4. As lições custam a ser percebidas. (The lessons are hard to be understood.)
5. Estes cursos custam uma fortuna. (These courses cost a fortune.)