I asked a friend who has some contracting experience about this. He had a different approach altogether: scribe cut 2x4s and nail & glue (construction adhesive) them to the concrete floor, then install a typical plywood subfloor. this would raise the floor on the high side about an inch and a half, and on the low side about four and a half inches. It'll be a bit tedious fitting each 2x4, but I think it'll turn out to be the most cost effective solution. Of course, either way of raising the floor means the doors need to be raised up. Since it's getting to be wintertime here in PA I'm thinking this is a springtime project.

If you're a DIY'er, you can use a self leveling cement on top of your ply subfloor, but you have to install a wire mesh first to act as it's skeleton, insuring it's stability. Remember, all wood moves, that includes your ply subfloor, and if you pour a self leveling cement on top of it, it will certainly fail. So you nail/screw down rows of wire mesh and then you can our your self leveling cement to give you a nice flat subfloor to glue down your parquet. How to achieve a truly flat subfloor/The Flooring Blog

Sure...you can shot blast the surface so that raw/rough concrete is showing. Then you will go ahead and do everything the way it should have been done. That is to say you will prime and then add the expensive microtopping to level the floor. Why microtopping? Because regular slab concrete is not 'good enough' to become a high-end finished concrete floor. A well finished concrete floor (no stain...just microtopped and ground to a polish) is $5-$7/sf (done professionally). If you want a professional to stain it, you can add another $2/sf. If you want a protective coating that will NOT stain nor etch (which all concrete will do) you can add another $2/sf. A clear coat epoxy is a finish that will have very little maintenance. A wax finish will require extensive maintenance (like every 6 months). A regular 'urethane' finish will require maintenance around about year 2...and every 2 years ever after. A temporary polymere finish (6months worth of finish) will require reapplication every 6 months. A stained concrete floor without a finish is going to be very splotchy...even if it didn't start out that way. As upset as you are right now, this might be a blessing in disguise. If you wish to pick another floor, now is a good time. With 6.5 years in the flooring industry, I estimate the average concrete floor will 'live' for 7 years. After that the homeowners become tired of it (either physically tired of standing on it; or psychologically tired of dealing with the look and maintenance) and cover it up. And yes...you should have done all the shot blasting, all the grinding, all the leveling with microtopping before staining. Again, it is because poured concrete is not 'ready' to become a floor. It is ready to be covered by something else...and that something else often includes self leveler or some other form of 'leveling' before any other rigid floor is put down. Carpet and sheet goods are the exceptions.

Or the cheapest solution of all: ignore the unevenness, drop down a vapour barrier such as 6mil poly sheeting and then lay the vinyl. Since your budget is so tight that $100 worth of testing is pushing to the brink, you might as well purchase the cheapest vinyl product and lose the warranty (as in ignore the flatness ratings). Put down the vinyl and hope for the best. No. I'm not kidding. Simply install the vinyl to the best of your capabilities (use the vapour barrier for $0.11/sf includes the Red Duct Tape you need) and leave it be what it is. You will spend more time and energy (and money) trying to figure out the work around when there really isn't one. You either spend money on the test or you spend money on the subfloor system like a sleeper system (more than $100) or a DIY option like Dricor (really not $100!!!). Or you ignore everything and lay the floor over what you have. Those are your options.