I agree with many of the points @Dave_C made.
Here's my feedback, experience with my layout/collection: I started my current layout around 2010 after a divorce, two relocations for employment and then needing and wanting to participate in taking care of my aging parents. My layout is 23 x 40, single main line 240 feet long with about 90% of the items on my original "must Have" list. Is it done today, no but it's 90+% there.
My two adult children nicknamed me "Bargain Man" more than a few years ago. For me that was a critical trait (ingredient) in building a layout and continuing to enlarge and rotate the contents of the "Collection".... Personally, once I got the plan pretty well documented after reading most of John Armstrong layout resource and planning books, I personally got much more interested in building the layout so that the collection would have a place to operate. Having large number of trains on shelves as trophies lost whatever attraction it ever had.
So Bargain Man, bought 99% of everything needed "used", all the Ross/Gargraves track, Ross Switches, Turntables, almost all the purchased buildings with the exception of a few from Menards. I'd say probably close to half of what I purchased was bought here on the OGR forum.
I shopped Craigslist, FaceBook marketplace patiently and regularly and bought several lots of dimensional clear, or near clear pine 1x4, 1x6 lumber and most all of the 1/2 inch and 3/4 inch higher grade plywood I required. Also purchased a bunch of Culled lumber from HomeDepot (which unfortunately isn't really available anymore).
In my case I decided early that this layout would be built in "irregular" shaped modules that could be removed and relocated in case my kids either wanted it, or wanted to sell it off. It took longer, but had some serious advantages. I didn't need the entire model RR worth of lumber, plywood, track switches etc all at once to get started. The other advantage, is I was able to make adjustments to the track plan as the build continued and my ideas evolved.
I learned how to make very realistic block walls hand carved, retaining walls, and mountains/rolling hills without buying any expensive items form the major scenery suppliers. I purchased around 25 NJ International Brass signal parts used here and then spent more than a few hours learning how to solder brass, and with the help of @stan2004 ended up with a wonderful ABS signal system protecting 11 signal blocks.
Was it worth it, absolutely. It's interesting that being cheap, trying to exercise patience & discipline paid some interesting benefits. I refuse(d) to pay market prices for many steam engines and 21 inch Pullman cars over the years. The blessing was eventually if I was "patient" and kept my eye on various sites I'd end up finding what I was looking for. Had I had no discipline, I would have just accumulated too many items too soon and then when the items on the "short list" became available, I wouldn't have had the funds, or would have to start selling items to raise cash.
The market, technology and our wants keep evolving, so I have learned that for me, there's a penalty for trying to force the issue and make it happen. One of the few benefits of age !!! Wisdom and a better perspective.
I also visited @Dave_C 's layout more than few years ago, after that visit I decided to go back to the Steam Diesel transition era and sold almost every diesel and modern freight car I owned.... Best decision I ever made !!
Here's some photos of the layout, seems worthwhile to add the photos so there's some context to the comments.