BE$T bang for your buck home improvement for home sale

Up here houses are going over asking, its ridiculous. I figure out 55 sq ft bathroom will cost approx 4k to do. Frickin pricey and that's using "above average" products materials and me doing the work.
I doubt it will add to the selling price we decided on BUT will make the sale easier.
It all depends on the market and a realtor will know.
Do a so called "open house" for realtors. Interview them and ask what they will do and provide. Ask them what you should "upgrade"?
Commision...are they flexible?
For me if I flex on my price to sell, then realtor best do the same.
Good luck