I currently have a 3 year old Lenovo thinkpad T470, with 8 GB RAM and 256 GB SSD. However my SSD crashed and now I am wondering whether it is better to buy a new laptop or only a new SSD (the costs are about a 100 euros). Any thoughts on this?
If you are happy with the machine there is no reason to buy a new one. However, if the SSD is completely gone, I'm not sure how you will get the key needed to reinstall Windows. Hopefully, you made a recovery USB or have a complete system backup. They used to put the Windows key on stickers on the machines but that was long ago. Still buying both Windows and a new SSD is a lot cheaper than a new machine. BTW, how exactly did the SSD fail (SSDs don't "crash". That's a mechanical term that applies to hard drives).
may not need the key. I had a couple that I replaced the drive on, install win10 I downloaded from microsoft and it auto activated. did not need the key. I cannot say it will work for all models but it is worth a try if not wanting to replace the laptop at this time.
I think as long as it the same computer, the auto activation will work since microsoft already has all the necessary hardware info from the previous activation.
I would get a new SSD. Check out Lenovo's support pages for how to install SSD on their laptops or there may be Youtube videos showing you have to install SSD on that particular laptop. I think if the copy of Windows on that laptop is associated with your Microsoft account, then Microsoft has a record of it. So, it should be easy to activate Windows 10 after installing to new SSD. Sign on with your Microsoft account at setup.