I started collecting slot cars (1/32 and 1/24) 'in earnest' in the early '90's, before ebay exploded onto the scene and completely changed the nature of collecting. I advertised want to buy and open to trades in the old Vintage Slot Racing Newsletter; set up tables at local toy shows, displaying some of my cars and 'want to buy' signs; there was a local flea market held every Sunday from which I bought a LOT of vintage slots very cheaply. As I was new to it, I bought just about anything, without a sense as to what was 'collectible' or 'valuable.'
One thing I learned early on from Philippe de Lespinay was to buy the very best possible examples of what I wanted, not basket cases (unless dirt cheap and a source of OEM parts to restore another car). I had picked up what to me was an unknown slot car, missing mirrors, windshield, most if not all chrome, and non OEM tires. I reached out to PDL to identify, and he said it was a 1/24 Monogram Lotus 38. Which was and remains (in complete/unmarred condition) one of the more collectible US vintage slots. Turns out they are not all that hard to find, but for some reason they were and are in demand. He told me that while a complete one has/had value, one like the one I found had little to no collector value and would be nigh on impossible to restore with OEM parts.
Pre eBay I was able to assemble a collection of about 700 largely US brand slot cars, either MIB or complete/mint/near mint. Most very inexpensively. I think the only collectible Cox car I never owned was the Gurney Galaxie, Otherwise I had most, if not all other Cox cars. And Monogram. And Revell, etc.
eBay changed everything. Almost gone were folks selling their old, or their dad's slot cars that had been stashed away for decades in basements, attics, garages, at give away prices. As in a complete and near perfect Eldon 1/24 Eliminator drag racing set for $15 from a yard sale. Two Cox 1/32 RTR Cheetahs in original packaging for $30 at a toy show. An original Buzz A Rama (Hoffman) pit box that had an IFC Cox 2E; 1/24 Cox Cheetah; 1/24 Monogram Snake for $75.
With eBay, with a few key strokes anybody could list their old slot cars with nothing more than a few key strokes, and collectors competed to own them. The days of 'deals' were all but gone. Not completely gone, but virtually so.
I cashed out, selling almost all my cars on eBay for much, much more than I had paid, and used the proceeds to pay cash for a fully restored 1:1 scale 1974 Lotus Europa Twin Cam Special.
Being a lifelong Lotus fan, my collecting was and is now limited to almost only Lotus 1/32 and 1/24 scale cars. Because I WANT them, I am willing to pay more than market for those I really want. Case in point: Policars/Polistil 1/32 Lotus Europa. Not a particularly great rendition of the car, and not the best runner in the world, and not particularly sought after. But as far as I know, aside from more recent resin builds or kits, it and the dreadful Artin 1/43 Europa are the only two 'production' Europa slot cars I've come across. I've paid more than market for the Policars Europas when I run across them simply because I want to collect them. Another holy grail for me is the Lotus Elan that was one of three cars that came in a 3 lane set sold by a Japanese company. The scale is between 1/32 and 1/43. Never sold in the US, and super rare, I never thought I'd ever be able to get my hands on the set, let alone just the Lotus. Amazingly, this past January, wholly by coincidence, I ran across the single Lotus and bought it from a guy in Ohio. It's a non descript car with unimpressive technology, but I paid likely more than most others would've for it.
I paid between mid and top market for the 1/24 Scalextric Indianapolis Special (Lotus 38), in complete condition, lacking only original packing. Why? Because I wanted it, and because PDL's advise to only buy the best resonated. I wouldn't have bought it if even one piece was missing.