For example, nowadays you could get a second-hand Ford Focus or Honda Civic for under £10,000 and you would be lucky to get a new one for less than £15,000.(and a fancy convertible could cost ten times as much)
On the other hand, a Baroche-Landau requires two or four horses and a groom, and a stable that can hold that number of horses, and a barn or a loft, and anything from 10 to 50 acres of land (depending on quality of pasture, season, soil, irrigation, hay etc). If Mr Suckling had a lot of land on his estate, and a large stable already, and four chaise horses already, the additional cost of a second carriage might not be that much to him, but if he did not, the total cost of keeping his carriage might be more than the cost of keeping a car.