Millermatic 200 fair price

Does "and everything" include a bottle with regulator and flowmeter? What kind of gas? Spoolgun? You can get a manual from Miller, in fact it's for the generic one or you can go to their manual page and type in the serial number of the machine and then you'll get a manual specific to your machine (Miller revs their machines all the time). The manual shows the machine comes with an optional spot pulse timer panel.
It looks like that machine has a 14-pin spoolgun connection.
OK, guessing. I don't know where you are, or if the machine has a bottle and a reg/flowmeter or a spoolgun. Assuming it does not, nor has the optional spot panel, I'd say $350-450.
Look closely at the mig gun. A gun that old might be absolutely beat to death. A new MIG gun would run you about $150.
If it has the bottle/flowmeter, I'd add $100. If it has a working spoolgun I'd add $200.
That's my best take. I'm pretty new to the wirefeed world, though.
Grant

At this site are several MM 200's for $300 with no cable, no gun and estimated repairs less than $300 more. There is a MM 250 for $900, used. A brand-new Miller 210 is available for $1250.
If everything is there and it works, I would say $400-$500 could be a reasonable price.

I am not sure. I will come out to look at it next week. They are asking $750, but obviously it is only a starting point.
Okay.
I got it. I will see. I think that it does not have a bottle.
You see, I now want to have a welder. I beat myself over not having bid on a nice big military surplus welder very recently. What an idiot.
i

Thanks. Makes perfect sense. Do they need 30A at 220V?
i

Read the manual! Since I looked at it and still have it, I took a quick look. No, it uses 40 amps at 220V.
When you go look at it, if you don't buy it on the spot and you take away unresolved questions, be sure to write down the serial number as any Miller person will instantly ask you for that number if you call to inquire about part availability. Number from the machine, number from the gun (if it has one).
This welder is a CV machine. It stabilizes the voltage with a large bank of huge electrolytic capacitors. Such large capacitors are known to dry out and fail anywhere from 10-30 years. Since this machine was last manufactured in 1991, it's conceivable that it may need some caps replaced. They might be expensive.
Miller blue paint is pretty easy to match. I found a can of Zynolyte Deep Blue that matched the color real well, but sadly that color has been discontinued.
Grant

should not be a problem for me, I have a 60A subpanel.
That's imporant to know, thanks Grant. What kinds of caps are those? (ac, dc, voltage, farads etc)
i

Forgot to say, I am now reading the manual that you mentioned.
i

electrolytic 15000 uF 45VDC Miller no. 084 087 from p. 53 of manual
GWE