We're considering the differences between registering with GS1 US, the official source, or buying through a reseller such as nationwidebarcode.com who buys codes from GS1 in bulk. The difference is $250 less to use the reseller
Depends on your marketing venues.
If you're using Amazon, skip the UPC as Amazon has their own coding system.
Buying a UPC from a reseller is tricky. If the reseller goes out of business or sells the same UPC multiple times (happens more than you think), then you'll have challenges.
Last time I purchase UPC codes, seems like it was $100 per 128 or 256 UPCs.
Whatever the cost, better to purchase UPCs from GS1, rather than a reseller.