Well, think about what you're getting.
The solenoid, you'll definitely want to keep.
The regulator, you'll probably want to keep, though it's a single stage, and you might get the urge at some point to substitute a dual stage, even though you'll see little or no difference. It's like deciding to buy a Mercedes when you have a really nice, comfortable, well-performing Honda Accord that honestly does everything you'd realistically want from a car. And yet, it's a Mercedes... $50-125 cost if you go there.
The needle valve, you'll get increasingly annoyed at over time, and will want to upgrade at some point. $50-75 cost.
The bubble counter is fine, though they do tend to crack occasionally. $5-25 for a new one. Interestingly, the least expensive ones are often as durable, or even more so, as the more expensive ones.
The check valve before the bubble counter might be fine, but all check valves will fail eventually. Faster when they're in direct contact with water. I'd recommend scrapping it to start. $5 to $20 cost, depending if you're willing to run it inline.
You'll need a diffusion method, $5 for a ceramic/glass diffuser you'll replace quickly, $25 for an Atomizer/Atomic diffuser you'll replace eventually if you have a canister, $30 for a DIY Grigg reactor inline with your canister (if you have one).
Check the date on the CO2 cylinder. It might cost an extra $15-30 for a hydrotest if it's out of date, even if you're swapping it at a welding supply shop.
If you decide to go for it, I might suggest offering $175, less if the cylinder is out of date.