it's worth noting that 40GbE is an absolute dead end in terms of technology, in the ISP world. Look at how many 40GbE members there are on many major IXes and other things. It's super cheap to buy an older Arista switch on ebay with N x 10GbE ports and a few 40GbE uplinks, because they're all getting pulled from service and sold off cheap. The upgrade path for 10GbE is 100GbE.

major router and switch manufacturers aren't even making new line cards with multiple 40GbE ports on them anymore, they're tech from 6-7 years ago. You can buy either something with dense 10GbE SFP+ ports, or something with QSFP/QSFP28 or similar 100GbE ports.

If you want something for a test/development lab, or are on a very tight budget, sure.

Meanwhile some budget homelabbers are jumping on the 2.5Gb bandwagon

The image is from 2012 and describes a topology, but not a technology.

Today you'd rather use Arista 7060, 7050cx orJuniper 5200 as ToR. You'd not build 1:1, but plan for it in terms of ports and cable space, then add capacity as needed.

Almost nobody in an Enterprise environment actually needs 1:1, unlike hosters or hyperscalers renting nodes to others. Even then you'd probably being able to get away with a certain amount of oversubscription.