This is interesting.
The current plot pice is 65 meebles per plot, per day. A 100 plot town costs 6500 meebles. 200 plots are 13000.
For 200 plots, it's only 13K a day, which is pretty manageable. You can earn 13K in 30 minutes easy.
You'd have to have 461 plots to get to a tax of 30K a day. By that time, your town should be pretty well flourishing. To break even there, 50 people can pay 600 meebles, 100 people can pay 300.
If you set your town tax to 150 and plot tax to 150, and all those 100 people have 1 plot, you can break even. 100 plots out of 461 should be easy enough to house.
Or, sell 2-plot plots, with plottax set at 100. Now they pay 350 a day, 200 plots out of 461. You get a 5K profit.
So long as you have a good amount of housing and lots of residents, your town should easily be able to thrive.
Plus, if you can manage to claim those 461 plots and spend 461K on plots, you should be financially stable enough to handle 30K a day.
(not to mention 30K isn't exactly hard to make. 30K in 30 mins is difficult sometimes, 30K in an hour is easy 90% of the time.)
all in all, I don't think it's needed. I've handled two 50K and 1 30K town at one time before - it isn't hard to make money if you manage your town appropriately.
Also, 300 meebles a day isn't really that high of a tax. Explain to your residents why the tax is there and how to pay it. Tell them to do /vote for a free 6K in a day. Some will leave, yes of course, but you'd be surprised how many people stay if you're nice and push them in the right direction.
I earned 70K yesterday from selling random crap I've hoarded to shops. People can make 200, 300K in a day in infected. Not to mention /jobs and /shop and /claim and /vote...
It isn't hard. Towny is the best and most efficient way for the economy to drain out a little.