I pay around 0,8% of my monthly salary (before taxes) for a month of free practice in the dojo. A decent dogi is about 2 or 3 times that, and a hakama is usually 4 times the fee.
The average seminar would run at around the same as 2 or 3 gi's, depending on the length.
Kyu-gradings are free and I believe the dan-gradings are free as well except for the fee to the Aikikai.
I make a decent living compared to the average person in Denmark, but it's by no means a lot.
From beginner to shodan would be around: 4300 USD, provided it takes around 6 years, 2 do-gis, one hakama (from 3.kyu) and about 150 $ worth of seminars a year. On top of this there is of course the travel and eating expenxes during seminars, and the weapons one might buy (jo, bokken, tanto and iaito) plus the wast number of extra laundrying one have to do