Railking steam with locosound. How much would you pay?

The answer depends on so many other things. MTH has made some great solid running models over the years that are worthy of upgrading to the latest sound packages. Has it just sat on a shelf or in it's box? Has it been run for huge amounts at a time at shows?

The less you pay for the engine, the easier it is to justify the upgrade. There comes a point where you should just buy a new one. Sometimes there isn't any others to buy so I upgrade.

I buy a lot of railking locos, some old locosound units, dead PS1, PS2.....I don't spend a whole lot on upgrades, until recently, I just started adding Dallee's reversing units.....I don't spend more than 60 to 70 bucks on them when they don't run this way I can keep the cost down on getting them going. It all depends on how bad you want a particular piece, for me....I wanted a good roster of railking hudsons, so being able to have running hudsons at a total cost of about 100-110 bucks a unit is a win for me.....

$50 to $100 if in operating condition and no damage.

Depends on engine.  Upgrade is easier since much of wiring and aux components are already there.  Just change speaker and add a coupler.  Count on the kit at $180 to 200 depending if your an MTH club member.  G

So the upgrade would not require a whole tether and wiring replacement? Thought more wires needed for the sepatare smoke element and fan power.

Loco Sound have smoke and tach reader for speed control.  Also have a Head light.  They are 5V connectors.  You might have to move around some wiring as Locosound can have the Speaker - being ground, while PS-2/3 is a separate speaker -.  Just compare the wiring to the upgrade kit, but otherwise the only thing it does not have is coupler control.  So you would add those 2 wires and the coupler from the kit.   You can move the wires out of their 5V connectors and into the 3V versions in the kit.  G