8 studios on Berlin Studio Map rent for €50/hr or less. Fotostyle Berlin in Alt-Hohenschönhausen is the cheapest listed at from €30/hr. These are published hourly rates from each studio's own site, not "enquire for pricing" estimates.
Ceiling height, cyclorama size, and location all push the price up. A blackout box in Lichtenberg or Weissensee will usually undercut a daylight loft in Mitte or Prenzlauer Berg, and a studio with a full kitchen, makeup room, and green room costs more to run than a bare shell. If you don't need a cyclorama or drive-in access, a budget studio with just a paper roll and lighting kit is often enough.
Several budget studios set a minimum booking of 3 to 5 hours, so the headline hourly rate isn't always what you'll actually pay. Check each studio's page here for the minimum before you book.