The main reason I bought the Mityva 7201 was to do oil change in my '00 E430. It had 4 years 50k miles free maintenance, the dealer charged $200 for oil change (8.5 quarts M1 0W40 and OEM cartridge filter) in 2004 and $250 now.
Bought oil on sale and with rebate the cost was about $25-35 for 8.5 quarts and about $8-12 for filter so the total cost was less than $50. I paid about $60 for Mityvac back in 2004-2005, which paid for itself with one use.
My brother in-law and I used the Mityvac at least 40-50 times from 2004 until 2010 when he bought one for himself, the cost per usage so far about $1-1.20. If it's lasted another 5-6 years, which I think it will, the cost per usage will be less than $1.
Oil change with a fluid extractor for many German engines is so easy, it siphons most, if not all, the oil via dipstick tube and cartridge filter is on top of the engine, so that changing oil and filter doesn't require a a person get under the car.
Other than oil change, Mityvac can be used to siphon any liquid and do brake flush. One of the most usefull tools I have, and even the initial cost is high the cost per usage is fairly low.