For example; were my car to be stolen the financial impact of me replacing it with another would be tremendous (a month of two of wages for a second hand model)
However if my bicycle were to be stolen the impact would be less so, a week or two of wages at best.
Was replacing a horse (back when horses were the most common mode of transport) equivalent to the modern day loss of a car, or a bicycle?
It depends on the breed and bloodline of the animal. Similar to make and model of cars today. The price could vary drastically depending on the use and stock required. Simply by comparing prices adjusted for inflation can be misleading, but gives some indication. If a horse cost ≈ £40 in 1900, the equivalent today would be into the thousands. So it wouldn't be easy to replace like a bicycle. But remember, most people bred their horses with others in their area, so the cost wouldn't necessarily be as much as purchasing a new horse from a breeder.