SonnyPhono wrote: I buy primarily from craigslist, auctions, ect. Therefor, the profit I make on any given phonograph is more than $100 or $200.
To me, that's not investing but backyard dealing. My definition of investing would be buying something at market value & the market value increases, not simply buying something well below market value then making a profit. You could probably make a profit flipping paper clips too, but I wouldn't call it an investment

Not that there's anything wrong with backyard dealing, unless you are deliberately going out of your way to rip people off. There's nothing wrong with buying stuff that's underpriced, but if someone finds a machine worth $5000 that was advertised for $1000, then feeds the seller a bunch of BS to get it for $400, they deserve to be hit by a truck.
After collecting for over 30 yrs, the sad realization is that only the rare desirable machines have substantially increased in value, and surprizingly portables too.
When I started collecting, an average HMV horn model would cost $600, and today I could get the same machine for $1200-$1500, which is probably in line with 30 yrs of inflation.
The average upright cost $75-$100, and now the same machines would be worth $200-$400.
An Edison Standard sold for around $300 back then, and now I'd still only have to pay between $300-$600 to get one depending on the source. My A100 DD was $100 back then, & I'd only get $200-$300 for it now.
These old prices were considered cheap at the time too because you'd generally pay a lot more buying through antique shops.
Your average portable on the other hand, cost from $5-$20 even from shops, and now the same machines sell for between $100-$300 or more, so it's really only these common portables that have increased 10 fold or more in actual value over 30yrs, making them the best investment of them all in the mid to lowend range of machines. Other mini machines like cameraphones etc have followed a similar path too.
Other than those, the only other machines that have skyrocketed is the rare stuff.
When uprights were $100, my 202 cost $325, which was considered a huge sum for a cabinet model, but what I paid was exactly what it worth at the time. I could sell it tomorrow for at least $10,000 because that's what it's worth, so it turned out to be a good investment.
It's only the other rare &/or early stuff that has followed the same path.
If I'd invested in filled a shed with tinfoil machines, lumiere pleated HMVs, Idealias, Berliners & portables, I'd be an extremely wealthy man today, but with a shed full of common & plentiful stuff I'd barely break even.