I used to work at a place that had the Weller WXR3003N. $3360 of pure joy. The one I work with now is a Weller WX2021N, which Newark has for $1400.

The tool quality on either is phenomenal, but definitely not necessary for learning on.

Some control over temperature, peak temperature hot enough to melt lead-free solder are really all you need to learn with. I don't want to be a neo-luddite, but you end up learning a lot of tricks with a sub-par iron that I rarely have to use with the high-end tool, but I'm glad I know. For instance, its rare with the high-end tools that I have to glob a bunch of solder onto a joint during rework, but I had to do that all the time with the cheap tool. But now, if I just can't get a joint hot enough to melt, I know that that is an option.