Melissa made 30 x 4 = <<30*4=120>>120 muffins
Together, Melissa and Sasha made 30 + 120 = <<30+120=150>>150 muffins
Tiffany made 150/2 = <<150/2=75>>75 muffins
Altogether, they made 150 + 75 = <<150+75=225>>225 muffins
They contributed 225 x $4 = $<<225*4=900>>900 to the fundraiser
#### 900