If we're talking about size 0 mailers, there are a few different places where you can get a box of 250 for around $75-$100 shipped before taxes.
Assuming you are registered for GST, you can get 100 for free with the shipping supply coupon, or 200 for about $27 ($97-$70 coupon).
For me personally, I buy them at Costco for $75 for 250. That means 200 has a prorated cost of $60. So the eBay supply coupon is worth $33 to me if I use them for 200 bubble mailers because instead of paying $60 at Costco, I pay $27 ($97-$70 coupon).
It varies by item. For example, the 8x6x4 boxes are $85 for 50 of them. That means I could buy 50 of them with my supply coupon for about $15 dollars. 50 of them at Staples costs $28. So my coupon in that scenario is only worth $13.
The wider point is that the kind of marketing they engage in with the supply coupon is offputting. If they want to give me a $20 credit for shipping supplies, just do that.
They might be better off partnering with somewhere like Staples and doing it that way. Staples stores are almost everywhere, and they already have the infastructure along with a wider variety of supplies. eBay sellers would also buy more supplies directly if they were appropriately priced, rather than inflated.
Ultimately, the program never made any sense to me. Is the purpose to make selling on eBay more accessible through providing shipping supplies? If that's the case, it's a failure because they aren't accessible at their price. Is the purpose to market eBay successfully by ensuring there is some level of standardization with packages going out useing clean supplies and the eBay branding? That's a failure as well, because no rational person is going to pay three or four times the price on supplies.
If it is just meant as a way to make some additional revenue directly off of sellers with no intention of creating value for the sellers, that is short sighted.
