If there are things we know about TV pricing is that they will always fall. Unfortunately, quality control is all over the place, and while a TV may be a good deal, build quality is simply unknown. A $2,000 TV may have an image worthy of that price, but may not have build quality worth half that amount. You don't even know until you've owned it for a year or two.
Regardless, how much you spend will help you get certain gains in image quality, and those gains are well established. Motion handling, black levels, shadow details, contrast, brightness, viewing angles... All these things matter. The room you put them in, your sources, and your demand for a great image are external factors which also must be considered.
If you intend to do nothing but watch sports (720p or 1080i), then you don't really have any need for a 4K display at this point. But, that's what they are. So, good image processing will matter. 120hz is a joke and irrelevant on a good display. Plasma never needed it. OLED doesn't need it. LCD still needs it because LCD isn't as fast of a technology as the others are.
Some people love creative frame interpolation (CFI), others hate it. The soap opera effect that it creates can be quite distracting from a quality image. So, if you don't care about that feature, it may be irrelevant to your purchase.
Mostly though, cheaper brands (TCL for example) have some better sets, but are more of a gamble on build quality. Some are excellent, some... not so much. Even from the same lineup.
Better brands like Sony, Samsung, and LG tend to consistently deliver the same product over and over again. But, you pay a premium to get there.
I'm of the opinion that spending good money on a good TV is well worth it. My family watches TV several hours a day. So, I want that image to be as good as possible for the room that it is in. So, yeah, likely a Sony X900 series or something similar for a bright room.
While OLED does reign supreme for image quality, at the size you are talking about, you have to drop more than $4,000 to get there, and it's understandable why they aren't even in the running.
I think the suggestion of waiting is always questionable. Since pricing will ALWAYS come down, sure, waiting will get you a better price.
But, if you actually want to get a quality 75" TV for that space, then just f'n buy it! If it costs a bit more than you intended to spend, then determine if that extra cash was worth it for the enjoyment you will gain from the TV over the years. I replaced a 65" perfectly good plasma with a $3,000 85" TV. Why? Because we enjoy it! That's reason enough to spend some cash.
Also, figure out if your size really is best for your room.
Certainly buying a smaller, cheaper, TV is an option. But, do you actually have some other location to move that TV to? Do you really not have ANY TV in that location already or is it an upgrade? I would have a hard time justifying any TV that isn't what I really needed in any specific location in my home. Stick with what you need would be my recommendation. I would also buy once, and enjoy it as long as possible.