When a child reaches kindergarten now, that child will have real issues if he or she cannot do these things:
Listen to and follow directions given by an adult who is NOT a parent or other familiar adult. A child who cannot grasp that the teacher is in charge and is "the boss of you" is not going to function in kindergarten.
Share toys and space and take turns with other children, giving up a desired toy or game to another child at times, even if he or she doesn't really want to give it up. The child must be able to understand the idea of "You've had that toy for a while now and it's Other Kid's turn."
Stop doing one activity when told to stop and move to another activity without melting down. This is very hard for many young children to learn. Why stop doing this fun thing/playing with this toy when I want to keep doing it? Only practice helps with this.
Move as a group from place A to place B and so on, when told to do so. For both the sake of doing activities and for safety (as in fire drills), kids must learn that when the class goes, they go.
Did you notice that not one of those things I just listed has anything at all to do with ABCs, 123s, workbooks or worksheets or reading?
Preschool teaches children the things I've listed. Preschool is about socialization and teaching children how to get along in a classroom setting within a group of children with a non-parent adult having authority. You can't teach that at home unless you run a preschool class in your house.
You are possibly thinking too hard about costs and thinking way too far ahead. Preschool now is not going to mean your child can't make it to college later because you blew the money on preschool classes.
There are so many options. It sounds like you have a dollar figure from one place and are basing your fear of the costs on that one figure. It can take a lot of research to find a cheaper preschool, or look for a parent-run cooperative ("co-op") structure, or one run by a school. Some even offer reduced fees if a family has real financial issues.
You do not have to do two or three years of it but at least one full "school year" before kindergarten would be immensely beneficial. I would bet that kindergarten teachers can tell the difference between K students who have had some preschool experience and those who have had none -- and the difference is not in how well the read or know numbers, it's in their behavior in a group setting. Please don't think of preschool as "wastage" as you put it, but as an investment in your child being ready for "big kid school."
Oh, and kindergarten teachers used to teach those things l listed above. But do not think that you can just let the K teacher do it now. The classes are too big, and the pressures from school systems to have kids doing more, sooner, is too strong, for K teachers to do a lot to teach kids socialization. The teachers have to focus on reading, writing and math much more in K now than they did when we were kids. That's why preschool is more important today.