How much does this cost

After these machines get past 5 years, they're usually not a good idea to buy after that unless you cannot do something without that specific model, or you have a purpose for it. If you already own it, keeping it going is not unheard of. Personally, my general rule is 1-3 years (or last year's model purchased refurbished from the manufacturer) for those who can't self-maintain, then once it gets to be ~3-4 years old those can work for someone willing to self maintain the system as it isn’t too tired yet. 6+ for specific use cases or legacy applications.

Like for example, if we relived my tech school memories of playing Halo CE and hosting class LAN parties with the help of a district employee at the time who was a student as well, I'd specify "Windows XP laptop" and leave the rest open to determination to the person taking part. However, I'd choose an E6400 (premium), or D630 (budget, no nVidia; those had issues with the GPUs) and an external mouse for my "play laptop" (back then, we did it PC to PC so there was no host system but we had to deal with port blocking), if we didn't have the XP 745's. The reason I'd want that is if you can't patch the game or do not know the patch level, a good base like XP is best. You probably couldn't run Halo CE well on a T43, but a solid Core 2 GMA950 Dell/HP/Lenovo may be fine.
(No, I'm not sorry about taking part in the class LAN party. I kinda used to be, but I realized everyone who "made it" has that kind of thing under them, so it's a badge of honor). My back would remind me really quick with how heavy those things are due to their brick like build with all of that magnesium and copper cooling, but it would be perfectly capable.