JamesLD

Unfortunately Bradley the silence speaks volumes - it's simply not possible to achieve any level of depth with the subscriptions offered by SquareSpace. It's bare bones functionality and from what I can gather through extensive reading and research, it has been like this from the start. Despite numerous requests from customers either here in the forums or directly via support requests, and promises of requests being passed to the new features development team, it seems that commerce is not going to be SquareSpace's focus. 
We've had a look at a number of possible workarounds using SquareSpace and outside code or payment providers but they're all a fudge and would not scale well with our business. I think we have to face facts and recognise that whilst SquareSpace has a lot to offer when starting out (ease of use, nice design), if you want to scale commercially you are at some point going to need to look at the alternatives who have built platforms from the ground up with ecommerce in mind. On that basis we are now actively looking at migrating over to Shopify which has a massive range of ecommerce apps to meet our subscription needs as well as many other features which should really be part of a SquareSpace's basic commerce offering.
I should add that I have had a support reply about this and in essence they've given up on me as a customer (it feels like) by saying we don't support what you need and understand if you want to leave - there's literally not attempt at retention or solutions being offered which suggests to me that they are not planning to add the features I need which is most disappointing. I am yet to see any feature request put through on this forum or directly via support over the years come through as an addition to the platform.
 

I have just had a support query answered on this and there isn't any way to offer multi buy/quantity threshold discounts.
I'm looking to offer a "buy 3 and get the third for $X" or X% off on our website but there is no way to do this. The benefit of having this as a discount option is the ability to manage inventory effectively so that if people buy 3 of our single products and receive a discount on the third, the single product inventory still gets updated. 
There was a suggestion to just offer a discount if someone spends over the amount that 3 products cost but unfortunately we have different variants (size) and it wouldn't be able to account for that. They also suggested adding a new separate product that was just the bundle - then buyers could selected the variants from a drop down but this doesn't work in practice as the variants end up being too many to manage AND they don't link up to inventory of the single product pages. This would then mean having to continually update the single product stock level after every 3 product set was bought.
I have asked this to be considered as a feature requested but based on the lack of responses on here to these queries that I can see, I don't know if it's a priority.
They have finally suggested looked at custom CSS code for this and I'm looking into this now and will report back if I get anything that may work. Similarly if anyone on here can think of a way to create custom CSS to implement these quantity discounts, please let me know!!
I know Shopify have their app store with products that offer this functionality - it's a pretty common e-commerce offering to be honest and I was quite surprised SquareSpace didn't have a way to offer it when I went to try and add it. Oh well!