I think it'd be really hard to prove any single tool provides you a specific productivity boost. Most engineers probably have a tool-set. Which means all those tools work together nicely. Taking one of them out, as well as adding one, might break the whole setup. Usually established engineers are not working in a vacuum, they already have their setups in place, so justifying a 3% extra cost might be very hard to justify for very unclear benefits, if any. I'm not trying to make a definitive argument, just some food for though.

That is not how it works, having a water cooler in the office increase the productivity 100x vs not having water, that does not mean you should pay millions for one. That is a myth invented by SAAS vendors and consultants to justify their sky-high price. The value offered of course factors in the price but many other factors too (scarcity of materials and resource to produce the good,cost of production, maintenance cost, cost of the products of your competitors, risk of vendor lock-in, etc)

I work in a very large enterprise that could definitely benefit from such a product, but at that cost I'm not even going to try mentioning it, it's never going to pass.

We have engineers in the thousands so that would be a budget in the millions per year, for a tool for which it's hard to demonstrate the productivity benefit over alternatives. Not going to happen.

It's not that the company can't afford it, but enterprises are strict when it comes to spending money. There are lots of processes, checks, and people that sign off.