When I checked in May, shipping for Jianken’s apparently awesome spindles was ~$500 to California. Have you checked on that?
IMO intended spindle use really needs to be considered when deciding what to buy. Most woodworkers and plasticworkers would likely be better off with a spindle that support’s 1/2" shanks (ER20) rather than one with a smaller collet that runs at speeds much higher than 24 kRPM. Most cutters for wood are only rated for 18-27kRPM operation. Also lower speeds are less demanding on cumulative runout and balance, so the detrimental effects of adding ATC are somewhat mitigated.
There are cutters available for the higher speeds in aluminum (to 100 kRPM) so the higher speeds can be productive. But, the higher speeds are more demanding on cumulative runout and balance, so the detrimental effects of adding ATC needs to be considered and may add significant expense.
Cutters for harder metals are typically rated for speeds lower than 24 kRPM. Here’s a Chinese spindle designed for hard metals.
Note that almost all Chinese spindles (except some Jiankens) are constant torque types, so they only provide the rated power at their maximum speeds..