I am tired of chasing a carrot, and even if that is a reality when dealing with laptop computers, in this particular case it sucks that I can't really upgrade my machine without spending a lot. Thanks for the detailed reply, makes sense but I don't know if I will be able to get 600 or 650 for this machine (nor where to sell it) and it will take a lot of my time to prepare it, advertise it, sell it, buy a new one and be up and running after all. The best option for just the SSD is the Aura Pro but for around $100 more, you get all the other upgrades. If you do get $650 for the old one, then it's roughly $369 for the latest 11' with 256GB and $449 for the 13'. You get a faster CPU, faster GPU (Iris), USB 3, longer battery life, faster 802.11ac wifi, 1 year warranty that can be extended to 3 years. Not only do you get PCIe SSD that runs at near 700MB/s as opposed to around 250MB/s: There's the latest 11' and 13' here on the refurb store with 256GB SSD: Your machine would sell for about $600-650. One thing you might consider is upgrading the whole machine. They are slower and will have some wear on them. I don't think buying a used Apple one on eBay is a good idea. The cheaper SSDs now use things like TLC NAND. Apple has also switched to PCIe now instead of mSATA in the old one. The blade SSDs have a custom shape so they only really work in Apple's machines, which is why you won't see many 3rd party versions. Is there any other option, than buying a used one on ebay?

I got the computer with those 64gb with the idea of upgrading the SSD later, well later has come, I am ready to move but can't.

I am wondering why is this escenario happening. More that the price of the drive, I can't really believe there are no other alternatives to my model! (at least I could not find one, crucial website says they don't have a replacement drive for my model). which I find ridiculous expensive, particularly in 2014 and for a relatively old machine. The only option I found is an OWC Aura Pro that cost more than 1$ per GB. I am looking to replace the small 65gb toshiba drive on my Air (model 4,1)

Ssd drive for macbook air a1370