Is skp model popular?

I don't sell Sketchup models, but from everything I've heard, they really aren't really the most profitable. The most popular file formats being sold here on CGT for furniture or architecture design is still .max/vray. By far. Last time I checked it was something like 31% of overall sales, with OBJ and FBX formats in a relatively distant second.

I don't think SKP format was even listed. However, don't let the statistic deter you if you have a good collection to sell. Just be sure to offer some exchange formats too.

CGtrader made a infograph a while ago with a lot of interesting information regarding different types of models and file formats.

https://img-new.cgtrader.com/uploads/blog/04db7daa-a47d-4188-bfdc-ae17e3ce0a89.png

Unfortunately, skp files did not even make the list in top 10 used file formats (and the number 10 is only good for 1% of downloads).

That said, that does not need to be a problem. It is important to just make sure you also export to other file formats. I myself use blender as my modeling software, and blend files only make up 1% of the files sold on cg trader. Even so, i have quite a few sales because i also export to OBJ (good for 18% of downloads) STL (good for 12% of downloads) and a few other formats.
only a few of my costumers are actually interested in the blend files themselves. they often leave them untouched.

So what ever you do, also export your files to different formats, especially OBJ. If you don't, you are cheating yourself.