Mini starter crapped out already

I think I paid $10 for the junkyard ones I took from Magnum engines, but I wait for half-off days at PicNPull. Measure the voltage right at the big stud on the starter, to the case of the starter. If it drops <10 V, don't blame the starter. Voltage drop could be in the ground connection from the starter's case to BAT-. You should be able to find the drop quickly. If >10 V, then blame the starter, which would likely be pitted contacts. Some rebuilders do a cheapie job, like re-using worn contacts, maybe flipping them around or such, but they do make the cases look new and shiny.