Heartless? What else would you call your mom??? I am pro slaughter... but not when it comes to a horse that lives to be 22 and given years of service to a person and than that person sells him off to get the last buck out of his hide. Make a buck rather than spend one. If your mom needed that $700 to buy a new horse maybe she shouldn't have a new horse. Not your horse that you have owned for 13 1/2 years that is now crippled up. Used up by the age of 8.... what a shame. I am not saying you did but most horses that are pushed too hard to young can't handle the stress on the joints, etc and end up lame young. IMO he shouldn't have been started on barrels till he was at least 5.
You have to do what you feel is right but as for me...my faithful friends will not have me turn heartless because of their age or their soundness issues.