Forklifts are big, heavy machines that are built in small quantities relative to passenger cars so production costs are higher. They also spend all day lifting big and heavy loads, and in your case are subjected to rough uses in demanding conditions. This all takes its toll. They also can't just be driven to jobsites, they need to be trailered or floated whenever they need transporting. Your forklift will go through tires, air filters, steer axle parts, bushings, mast chains and bearings, not to mention regular oil changes and grease jobs, and other random breakdowns like fuel systems, electrical, radiators, you name it. Cars have it easy by comparison.

I would not use air-filled tires in your application. Start with a pneumatic tired truck, and either get the tires foam-filled (it's actually a urethane rubber product) or get solid softys. Any industrial tire supplier should be able to help you select the best tire for your application. But again, they are not cheap. count on at least a few hundred per tire.

I had a customer get angry with me because they bought a Crown RC3020 from my employer a year and a half ago and had to pay $150 for a tech to fix a broken wire. They put over 1000 hours on this machine and refused to get a single PM or lifting device inspection from us. And they still complained over $150! We do all we can to keep customers happy but They need to have realistic expectations of the machines they use and of us. People are always surprised to learn how much machines cost, it still surprises me when I pick up a flier from an auctioneer and see what old used machines are selling for. But production costs for small volumes of parts are high and they have a very demanding job to do---Forklifts are expensive.

What you might want to look into, again, is getting a new or slightly used machine from a major dealer with a full maintenance contract. This way you can look at a fixed monthly operating cost for your business and the only surprise expenses you will face will be damage and wear & tear. They'll come in and do oil changes and grease jobs and inspections for you so you don't have to worry about it.