I'd say whatever your reasonably comfortable spending should be the limit... i.e. there is obviously no set limit.
Some folks have lots of money and the thought of spending many thousands doesn't fly, others I'm sure have excellent tables in more modest homes for example. It's all about priorities.
I'm moving from a Scoutmaster to a Raven AC, (finally decided on that over Raven One), as over time I have changed my perspective on upgrades. I used to like incremental upgrades but now think it makes more sense to take a big leap to your "dream" component, (assuming you can fund it), and stay there for much longer. Fewer bigger steps if you will. No right or wrong way, just my opinion.
So, for me the cost of a Raven is about what I'd look at as the upper end. If I can't get what I want out of analogue for that I ain't getting it as I don't see me ever sinking more into a table. I may change it one day but for me I think that is more than adequate and enough that most of the general population would think me an imbecile. ;-)
I'd say, get into a good table/arm combo in that range, particularly if you're lusting after it anyway, and enjoy it for the long haul. You'll have a solid cornerstone to your system and appreciate improvements elsewhere.
Best of luck whatever you do.