A reviewer wrote "I can see why it didn't do well at the box office", but I beg to differ, for the sake of conversation :-)

For what it was (not a very good cop movie), it returned $20M on a $7M budget - that's almost 3x ROI.

Of course, compared to other action movies released in 1988, sure, it wasn't steller...but check out these numbers...

Rambo III brought in $189M on a $64M budget, 3x ROI.

Die Hard brought in $140.7M on a $28M budget, 5x ROI

Bloodsport brought in $65M on a $1.5M budget, 43x ROI

Dollars are one thing; ROI another. If you were putting up your own money to make a movie, would you prefer Rambo's numbers or Bloodsport's numbers...?! It depends. Most people would rather make $120M than make $60M, that's fair.

So, in terms of dollars, sure, it didn't sell a lot of tickets and, by that measure, I'm happy to agree it didn't do so well; but, in terms of ROI (which is what producers are as concerned about, if not moreso), to perform on par with Rambo III, a fine installment to an established franchise, is not so bad after all. And, to be sure, the budget could be lower because, let's face it, Carl Weathers does not draw like Sly!

As an interesting digression, compare the numbers between Cobra and Beverly Hills Cop:

Beverly Hills Cop (1984) brought in $316M on a budget of $15M, for a heft 21x ROI

Cobra (1986) brought in $160M on a budget of $20M, for a solid 8x ROI.

What's interesting about these two films? Stallone was originally signed on to play Axel Foley in BHC, but his script massaging blew the budget far beyond what the producers wanted to cover, so they fired Sly, brought in a young phenom in Eddie Murphy, scaled back Sly's explosions and car chases, knocked it out of the park.

Sly, ever confident in his vision of things, would eventually find the producers to greenlight his project, which became Cobra. Bigger budget, didn't do quite as well.

One more juicy note (that has nothing to do with box office numbers - Sly's wife (at the time) Brigitte Nielsen appeared in Cobra with him in 1986; she also went ahead and appeared in Beverly Hills Cop 2 in 1987, the year they got divorced! (And there's a cute scene in BHC2 where Eddie Murphy as Axel pauses by a poster for the movie Cobra at Billy Rosewood's place - bwahahahahaha!)

P.S. This kind of conversation/debate/mud-slinging fight is going to be increasingly relegated to the bygone era of ticket sales, as online streaming is displacing "box office" and there are no longer tickets sales to tally. We're in the midst of a paradigm shift as more and more movies release online only.