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.