Can I have suggestions from other gardeners about which planter pot materials are the most durable, and still lightweight --(I'm in zone 6, which means cold snowy winter temps.) , AND the best, reasonably priced sources for them? Some of the prices I'm seeing for a large planter (maybe 12X12) are more than I want to pay. Thanks for your input!

I've had good luck with these resin planters from Lowe's. I'm in 7b, they're still good after several winters. I did drill a lot of extra holes in the bottom to improve drainage.
https://www.lowes.com/pd/allen...

It depends.
The best ones I've had were 5G used ice-cream buckets at $0.50 each we bought in 1999 and some are still in use. I also have square 30-35G storage containers from Walmart at $12-15 that have lasted over 6 years. The blue ones are best, but I can't tell you why. I've used really cheap wash-up buckets, but they fall apart after a couple of years. Garbage bins are generally food, as are water barrels, but they're more expensive. Last year, I tried fabric grow-bags, and so far, I'm happy with them.