When we first started HI Silk, a (now former) friend said, "Well, I can get a silk bed set online for £20"
"Baah! Fool! Be gone with you!" That's what I should have said. Shockingly, this isn't what ended the friendship, but the signs were written on the walls. Beware those with bad taste in fabric. Instead, we took the gentler route, and carefully explained the difference, as i shall do for you now, you lucky devil.
First off, silk is a natural fibre derived from silk worms, whereas satin actually refers to the weave. So, where it gets a bit confusing is that silk has a satin weave, but the term "silky satin" isn't actually silk. If you see something marketed as a "silky satin pillowcase" it would be a man-made fabric and not the natural fibre silk worm silk.
Still with me? OK. Next, silk is very durable. The higher the momme count, the more durable it is. Our bedding is 25 momme, which is higher than a lot of our competitors. Satin tends to be less durable as it snags easily and wears quite quickly. Polyester is the satin pillowcases also plays a major role in this and also cause it to be irrespirable. Unlike a silk pillowcase, which is very breathable, and doesn't produce much friction, so can help regulate your temperature and reduce frizzy 'bed head'.
Now, I'm not going to sit here and give you an unbalanced evaluation. In satin's defence, people find it easier to wash, and and the bargain hunting friend said, it is cheaper. But, I would say that your relationship with silk bedding should be a reciprocal one. If you look after it, it will look after you. You can hand wash silk bedding, but it can also be machine washed at 30 degrees celsius or lower on a delicate cycle. As for the price, I like to think of it as an investment into your future happiness.