Agreed. Personally, I would love to move to Denmark, and I am actually on the job market right now (I do scientific computing with Python and some related data engineering tools, so I have no idea if I fit the OP's company) but my immediate instinct is to be really skeptical of this.
For me to feel like a job offer to Copenhagen is attractive, the take-home pay needs to be similar to what it would be in Boston in the US ... so mid to high 100k USD range of gross pay, say something close to 100k USD take-home pay, which roughly corresponds to a take-home pay of 688k Danish krone per year. With high taxes there, I'm guessing this means a salary of greater than 1MM krone/year to be roughly equal to a competitive offer in a mid-cost urban area in the US. And if it is in the finance industry as the OP suggested in another comment, then there should be some opportunity for profit sharing as well.
Cost of living doesn't factor into this so much, though cost of living in Scandinavian cities is pretty high. There is career risk and visa / tax hassle to worry about, relocation and housing costs, and the usual start-up risk. It's not at all the same as taking on a risk in the Bay area, where there are many jobs to switch to if your company doesn't work out.
I think a lot of start-ups don't consider these things, and often they don't have to consider them because there's a line of schmucks down the street waiting to work for them.
But if you are a thoughtful person and you consider visa risk, tax risk, career risk, relocation risk, regular start-up failure risk, etc., then for a job like this you might even expect a significant premium when compared to US-based jobs in the same field. A lot of European start-ups, I find, don't fundamentally think this way, and they expect that American workers should be happy to accept "European" salaries, which are then taxed at a higher rate, all while you're bearing many additional risks.
Unless your personal preference function puts a huge, huge premium on the status of "living in Europe" then it's probably a bad deal in terms of net life happiness.