There's more to using sub 1mm cutters than just spindle speed.? While the speed n feed calculators spit out Rpm n feeds suggestions they don't and cannot take into account the machine your using.
When you get into miniature cutters then vibration is your biggest enemy rather than lack of RPM. If the machine isn't stiff enough then you won't achieve the feeds and therefore Rpm will need to be lowered to match what machine will allow.

I pretty much exclusively cut aluminum and have used cutters ranging from 0.1mm up to 16mm with 24K Chinese water-cooled spindle without any issues.
60K spindles come in various types but direct drive high-frequency motor types are very expensive, as are the air bearing types. So you may be better looking at the type which use a separate motor like found on engraving machines. 60k and 100k isn't uncommon in engraving.