Not to take away from your main point, but the capitalized total cost of ownership for a pony is _much_ larger than $1000 (which, by the way, is the price for a not-very-good-natured pony; breeds with nice temperaments cost a lot more according to https://pets.costhelper.com/pony.html ).

Doing some quick checking, food for a pony is ~$1-2k per year. Lodging is $2-3k per year. Basic preventative veterinary care is $1k per year; if the pony gets old this could get a lot more.

That's $4-6k a year for upkeep, and ponies live for 20+ years. So the actual cost of a pony, even with discounting and whatnot for future dollars, is probably at least $50k, not $1k.