Why are mares in foal so cheap?
IMPORTANT NOTE: This question is asked entirely out of curiosity. I'm not intending to actually buy for at least 5 and possibly as many 10 years, and I doubt I'll buy a mare in foal when I do.
With that out of the way: while browsing horse ads and daydreaming, I've noticed that mares in foal seem to be MUCH less expensive than their non-pregnant counterparts. More than once I've seen two horses of similar coat, age, breed, and conformation, neither of them with a bloodline that's obviously better or worse than the other. But the one that's not pregnant will go for $20,000 to $40,000, while the one that is in foal is only $2,000 to $15,000 in comparison.
Why is that? Is it the cost and risk of caring for a pregnant mare? The fact that a foal is several years of work and expenses before they can be worked? Is it just that mares with the training needed for riding and showing are less likely to be bred?