10k is insane, i'd want at minimum a seat with that. I know we're hitting inflation, but that's criminal. Sort of like those idiots charging a premium for standing desks in offices, almost as bad as those who are willing to pay the price.
Man invented the chair so he could sit. Then he invented the riding mower so he didn't have to push his mower. Unless you have some ailment preventing you from sitting, I would 100% get a rider. I've never seen a standing mower in use other than commercial mowing where the business owner probably didn't care about the comfort of his mowers.
You have a home, a roof over your head. Do you sleep outside on the grass and dirt? No. You sleep inside, in your air conditioning and furnished home because the end goal of man is to make life more comfortable. You want to exercise for your health to stay in shape, sure, I get that. But if you're taking steps to actively make yourself less comfortable, you're an idiot and if natural selection had any say, you'd be removed from the gene pool.