... when the core business is some digital product?
Investing time in tooling, tests, refactoring and so on, adds more value for the business?
Thinking on the long term, if I spent some time updating code, refactoring, writing more tests, this contribute to raise more confidence in the code/product delivered, avoid bugs and other problems, and it seems to reduce later efforts.
What do you think?
Yes, dev productivity has a definite business value. The faster you can respond to the market and the customer demand, the closer you stay to the top of the customer's value curve. But it also has a cost. Investments in tooling, quality, etc. Also the way you code can increase costs (as I've experienced first hand from legacy systems), requiring more investment. Taking these things to the extreme, the cost could be too high for the product to be profitable.
There are no canned answers to this conundrum. The best strategy is to know your customer's business and understand what they are asking to the best of your ability. After that, it is a matter of properly using all the technical tools at your disposal to meet their need, which comes with experience.