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NASA did the impossible 50 years ago -- putting a man on the moon -- and achieved a similar feat 50 years later ... putting on a spectacular Apollo 11 celebration for relatively pennies.

TMZ's got the receipts from the blowout celebration this week on the National Mall ... and according to federal procurement docs, NASA doled out only $1.4 mil for a series of special events ... that's like a small house in Burbank, maybe.

Now, get this -- at it's time, the Apollo 11 mission cost $25 billion -- a number experts say would land just south of $300 billion in today's dollars.

This week's events include hands-on exhibits, live performances, speeches from moon experts and a 363-foot projection of the Saturn V rocket on the Washington Monument. This showed how space exploration affects our daily lives and can inspire the next generation of explorers.

Federal procurement docs show NASA spent a little over $43,000 back in 2009 for the 40th anniversary of the moon landing ... a small celebration on Capitol Hill and a White House photo op with astronauts Buzz Aldrin, Michael Collins and Neil Armstrong alongside Barack Obama. That was like a backyard fireworks display compared to one at the Statue of Liberty for July 4th, which is what's going down this weekend!!!