..I found a Sandvik Coroman 3/8" endmill and it cost $190~...
If it's from Sandvik I'm guessing that was an insert end mill? $190 sounds about right for such a thing: 3/8" is awfully small for insert tooling.
You can get new HSS Niagara's from Amazon for $20-$30 ea in that size, e.g.
Niagara Cutter HSS Square Nose End Mill, Uncoated, 30-Degree, 4-Flute, 2.875" OAL, 0.375". A bit more for carbide.