The individual boarded ws2812b’s are for auction on ebay. I participated in multiple auctions and got most of then around 50% of the ebay (China) price. If you can wait, you can save a lot of money. But the single pcb’s have their pros and cons. As wearables the are very flexible to apply. For high amounts they are a pain. Not the soldering but the prepping of all the single strands of cable.
Thanks @Mike_Thornbury
I see that Aliexpress does have them at 20$ however, the shipping costs to Canada adds another $20 to the total costs !!
You also pointed to world semi that actually manufactures them, have you purchased directly from them ?
Hi @Kenneth_Tan ,
Yeah, I did actually get them by auction at that price and I lost quite a few bids before I finally got those (Probably to you… 
And I do understand the pros and cons about them. However, I now see a really big CON if they are going to die on me in numbers due to soldering !!!
I only purchase from WorldSemi.
They are quick and cheap and always have stock. as to shipping costs, that was one vendor -shop around. Lots will offer cheaper shipping than $20
Jp, make or buy some flux. That helps with soldering. No led lost after using flux. And very clean solders
Hi Kenneth , what is Flux ?
Google it. It makes the flowing and sticking of solder so much butter. No more pins with solder stuck together.
You can make it yourself by grinding up some resin and dissolving it in 》96% alcohol.
Lots of tuts on youtube.
I had the same problem , I took a meter length and cut it up to make a matrix and some leds would not work , but when you touched them they did…hmmm , anyways I found that the actual tabs on the back (copper thingies) were dodgey and not making contact after soldering … I don’t know woth checking out though