One pet peeve is folks hogging an equipment - especially for the wrong purpose. Sitting at the bench press equipment and doing seated curls. Just one of the reasons why I train at home.

I don't have numbers, but it's definitely costly to buy new.
For home training, you need to consider space too, so "more is not necessarily better". I say keep it simple and stick to the basic: squat racks with safety bars, a bench, adjustable dumbbells, several bars and plenty of weight plates. Add maybe a chinning bar. You could do many exercises that target all muscle groups with those.
If you're handy with DIY projects, you could even build your own equipment.
Try to find and buy used weight plates. Even the heavily rusted plates can be cleaned and refinished easily.