Probably not that much relatively. Specifically the Perseus cluster reported on here has a mass of around 10^15 solar masses in total. Of that ~10% is in the f

Probably not that much relatively. Specifically the Perseus cluster reported on here has a mass of around 10^15 solar masses in total. Of that ~10% is in the form of stars, 20% is intergalactic gas and the remainder is dark matter. The report here says 1.5 trillion of these stars in this cluster which is ~10^12 solar masses (assuming average star mass is similar to the sun's.) So the newly observed stars reported here are around 0.1% of the total cluster mass, or around 1% of the total mass of stars in the cluster. All very approximate of course.