Many computer vendors have outlet sites, where you can buy cheaper laptops that are unused. And they often have intermittent sales, so worth waiting to see if prices drop even more.

E.g. http://outlet.lenovo.com/

Alternatively, Thinkpad laptops specifically are pretty well built, and easy to replace parts. They have a downloadable manual on how to do so even! So you can just buy one off ebay for $150 and it'll probably work just fine, and worst case you can replace the hard drive.

This is specifically Thinkpad; generic Lenovo consumer laptops are likely not designed for maintenance.

To really answer that question, what are you going to use it for? That drives the memory, display, storage, OS, etc.

That said, I usually recommend a Thinkpad T420. You can usually find some decent refurbished ones on eBay.

For the last few years Ive used new 15'' Macbook pros. I switched to a 2012 macbook air a few months ago.

Its been so good in comparison, despite the smaller screen, that Im now thinking of buying another and saving it for later use after this one dies.

I was lucky enough to have a stash of Nokia E71s that lasted years. These earlier model airs remind me of them. They simply work, and do the job without fuss. Battery is still fine too.