This article is from the Bulgaria FAQ, by Dragomir R. Radev firstname.lastname@example.org with numerous contributions by others.
(by Vassil Peychev), last updated: 01-Jan-1994
You can buy any amount of dollars from a "Change" office, which are
everywhere in the bigger cities. However, to be able to get the currency out
of the country you need a document, certifying where you have it from - for
this, you need an international passport (no visa), and the limit is 10,000
lv. However, you can usually get away with a slightly higher amount, and in
my experience the customs officers don't care. If you bring currency in, you
can take it out with your entry customs form, so don't throw it away!
P.S. Some numbers look suspicious to me (e.g., prices for a round-trip
travel with a stay up to 1 year are the same for Economy class and for
Business class; also, two one-ways are cheaper than one 1-year round-trip
travel). However, this are the prices which the agency my wife works at
received officially. I might ask her to verify some specific figures if
there is interest.
Also, soon the limit will be 50,000 leva, and if you need the money for
medical care abroad or for education, there is no limit - but I guess this
would involve some unpleasant amount of paperwork.