Great find - but don't get too carried way with its value.
There are differences in the pumps across years, 72-73 different than 74, there may also be a difference between the 72-73 "cone".
Plastic runners in 72, aluminum in 73-74
Different throttle body in 72
They made ~44,000 tii using this fuel injection system.
Used pumps are getting harder to find, but they are available. A complete system on ebay for $1600 or best offer and has been for sale for 6 months as they started at $2500.
www.bmw2002faq.com has individual pumps for ~$400 used and complete sets for $800-$1500 in the past. Rebuilding a pump is not a DIY project and costs ~ $1000. Most loose used pumps and systems were removed because they needed to be rebuilt and it was cheaper to convert to carbs or find/buy a new pump.
The $25K pump you found is rare, was used in Porsche race cars (935 and 911 SCRS), is New Old Stock, and has been for sale for a long time.