It kind of went under the radar, but there's now a 50th anniversary edition, with everything up to the latest JJverse film. I've just had too many other things to put money towards so far.
The most recent revision was the 2016 edition. Before that was the 1994, 1997 and 1999 editions.
Sadly, the 2016 edition didn't get much of a print run and the costs on the secondary market for it are astronomical, with used copies going for around $470.
https://www.amazon.com/Star-Trek-Encyclopedia-Revised-Expanded/dp/0062371320
Some of it is my preferring to 'hunt' them down instead of just click-n-buy but finding copies in good condition online often means the price is 10x higher than what I can find in a physical store. The 3 books I got (yesterday) set me back a whopping $7 total. You also have to hope that the pictures are accurate, aren't hiding any damage (missing /torn pages, writing etc). Sure you can file a claim if the listing is inaccurate but that's a pain.
The encyclopedia, 1st ed hardcover (like mine in the picture) online is usually somewhere around $30; and as you can tell by the "picture" I have no idea of it's actual condition.
I mean realistically no, none of the books (save the 2016 Encyclopedia*) are particularly "expensive" online; usually between $10-30 for a hardcover, or around half for paperback. I could certainly "restore" my collection in under a day (less shipping time) and be done with it; but going out and digging through shelves and vender stalls is part of the fun.
* A few years back when I first found out about the 2016 edition, you could get it on Amazon for ~$150. I really should have gotten it then (note the "used" versions on Amazon are actually the earlier versions, not the 2016).