As others say, it varies from shipper to shipper, based mostly on volume, partly on typical package weights and zones (in general, the larger the packages and the more distant the zone, the bigger the discount). But I suggest you look at FedEx SmartPost list rates for starters, which are published (though I'll tell you below what they are). SurePost competes directly with SmartPost, the only difference being that SmartPost uses an entirely different distribution network (hub to hub) from FedEx, while SurePost uses the UPS network until the "last mile," for which both use USPS "DDU" drops. SurePost differs from its predecessor, UPS Basic, in that some UPS Basic packages were delivered by UPS drivers, whereas 100% of SurePost packages are delivered by the US Post Office.
As you get very close to 10 pounds, SmartPost list rates start to get higher than corresponding FedEx Ground rates, and eventually are higher (that's to encourage shippers to use FedEx Ground/Home at higher weights), but at all lower weights and zones, they are identical, to the penny, to FedEx Ground/UPS Ground commercial rates. The difference is that, if you ship FedEx Ground to residential addresses, you pay a hefty "residential surcharge" ($2.55), whereas there's no residential surcharge on SmartPost rates.
Incidentally, as you probably already know, FedEx Ground and UPS Ground list rates are identical, for every weight and every zone, and the essential difference between FedEx Ground/UPS Ground rates and FedEx Home rates is the residential surcharge, which applies to all FedEx Home packages but applies to FedEx/UPS Ground packages only if they're actually shipped to a residential address. Another difference is the "delivery area surcharge," which applies mostly to rural addresses, though not entirely: last I checked, 25% of US residential addresses were subject to this surcharge, and a small percentage of "super rural" addresses were subject to an additional surcharge. I'm not entirely sure about the following, but I believe SmartPost customers are NOT charged any "delivery area surcharge," though I have little doubt that the distribution pattern of shippers is taken into account by FedEx and UPS when they set discounts. Shippers who sell mostly to rural customers probably get a smaller discount than those who ship primarily to urban addresses.
SmartPost list rates are discounted -- fairly heavily, I'm told by some savvy consultants, though I don't know the percentages. Since SmartPost (and SurePost) packages tend to be light weight, what is more important than the percentage discount is the "floor." What that usually means is that, no matter how big the percentage discount may be, the shipper will not pay less than the 1-pound, Zone 2 list rate (there is no Zone 1 -- don't ask). That is common in UPS and FedEx Ground contracts as well. That does not mean that FedEx and UPS never discount below that "floor." They do. But they tend to dig in their heels a bit more when a shipper wants to reduce that "floor."
All of these rates get very skewed if you get information about very, very large shippers -- Amazon and the like -- who drive such hard bargains that I suspect many carriers end up taking a loss on their business. I think a better barometer is the category of shippers just below the Amazons. There are many hundreds of large shippers out there, far smaller than Amazon, who nevertheless ship upwards of 10,000 packages a day -- some ship many more than that. They get large discounts, but I doubt they get much off the "floor." About a year ago, I saw a contract between FedEx SmartPost and a shipper that shipped about 20,000 packages a day from Cincinnati. It had a blanket 30% discount from list, with NO discount below the "floor." It had some volume incentives in the contract that might have lowered it a bit, in theory, but I reviewed about 18 months of actual charges and not one of those many thousands of charges varied by a penny from the 30% discount (subject to the floor). I'm sure there are shippers with bigger discounts out there, though I'm sometimes suspicious of shippers' discount claims (especially after reviewing the actual billings of this large shipper). I've learned that shipping managers are not inclined to tell others their UPS/FedEx discounts. They're prohibited from doing so under their contracts, but I always get the feeling they wouldn't do so anyway, because they want people to think they're a big deal, and "big deal" means "big discount" in the shipping business. Asking them about their discount is almost as if you're asking them the length of their penis, and there's roughly the same amount of exaggeration in both cases.
I hope this helps.
