It easily costs more than the flooring material is the only guide. And it depends on if that includes undercutting the doors, removing and replacing the baseboards, adding quarter round, or a bunch of other stuff that is "prep" associated with the project.

What about just for application of self leveler?

Just finished a big leveling job using Ardex primer, V1200 self leveler and Feather Finish to smooth edges and make fine adjustments to height. Here's how to calculate a price.

Material: Measure and calculate the average deviation from level, determine how much product will be needed to bring it to level, multiple the number of bags times the cost per bag, add for primer, Feather Finish and other incidentals. Tally material costs and mark up for overhead and profit.

Labor: Determine what kind of preparation is required (cleaning, grinding, applying primer), guess how long it will take to mix and pour self leveler, guess how long it will take to apply Feather Finish and grind down high spots, add for labor to acquire and deliver material, add materials and labor for any protection and cleanup required. Tally number of labor hours, multiply times hourly rate.

Add together cost of materials and labor and provide client with quote.

Easy peasy!

My floor installer said he is going to charge me $20 for every bag of leveling material he is going to use. We ended up paying $4600 in total. And that was for 4500 Sqf.

The cost is directly proportionate to the unlevelness of the existing floor.

You need to get more quotes. If you can estimate the material, including all components, you can offer that info when discussing the job with other contractors. This should help them know you expect a quote based on realistic costs. With all the money you'll end up saving you can consider an engineered hardwood wide plank. Possibly one of the European Oak products you can see everywhere.

All types of flooring require the subfloor to be withing 3/16" in 10" flatness. It doesn't matter what material you are talking about. The subfloor has to be flat.

On the other hand with an uneven floor you always will know there your marbles will end up.

No arguments here with the need to level, I’m just trying to get a ballpark sense of cost per square foot (or time per sqft) because the quote I have seems very high (~40hr for 600sqft that is part way demoed already, most of which already had LVP on it). Of course, I’ve never done this before, so maybe it’s an arduous process.

Thanks to everyone for info so far!!

It is difficult to discuss the fairness of the price without having a lot more details. Self leveler over a slab is a whole lot easier than self leveler on a second floor.

It’s a first floor subfloor

It used to have a kitchen on it, but that has been demoed and removed.

$3.00 per square feet per 1/8" build.

So I paid $1 per Sqf. I’m in South Florida.

Self leveler alone is $1.00 per square feet for 1/8" build. That's one bag that covers 40 square feet. Self leveler does not really self level. you have to work the product to level: screed, aerate, trowel, etc. . Plus you need to scrape down high spots before it hardens before applying the next coat. Feathering the edges is not a walk in the park either.

Anyone willing to share an average labor hours per square foot with me? Just imagine an average job

"The quote I have seems very high"

Get more quotes.

That's why the OP gets multiple quotes. There are guys who throw out a quote without considering costs. Maybe, given their schedule, that works for them. When the customer knows the materials costs through his own investigation or purchase, his problematic contractor indicator can be working when he talks to these guys. There are contractors to avoid for various logical reasons. And some that were told to stop and leave the sight. Many guys to be avoided as you try to find a fair competent person to do a specific job. Luckily, the work can be done by any number of people in most cases.