Someone asked about clutch replacement costs and if $1800 was out of whack. It's probably about right for a dealer to do. Single dry clutch with pressure plate and bearings is 250-500. Dual stage dry clutch, PP and bearings is 600-1000. Depending on quality, brand and where purchased. For instance, the clutch disc for my Ford is $85 from the low cost EBAY types. The FNH Heavy Duty disc is almost $200. It is also 2x the thickness and made with a far higher quality material. You get what you pay for is sometimes true. To change the clutch, the tractor has to be split into two pieces - engine half and transmission half. Labor to do that is 8-16 hours depending on tractor model etc. So if you spend $500 on parts and supplies and 10 hours of labor you are pretty quickly up to $1500. So an estimate of $1800 is not out of line.
As far as reliability, there is no significant difference between any type of transmission when used correctly. We all know what happens with a teenager and a stick shift car, some tractors are operated by people that run them the same way. (no, not any of US!) Aggressive use of the clutch and gears can put a lot of shock load into a transmission and drive-line. That means that a gear tractor can be damaged more easily than an HST by enthusiastic or aggressive use. So while by design there is no inherent reliability issue with any type of transmission, a gear tranny can be damaged by abuse easier. (Inexperienced operators often abuse gear transmissions, especially the clutches, unknowingly)
Are gear transmissions cheap to repair? No. Repair costs are dominated by labor. The labor to fix a gear transmission is basically the same as any other. Parts may be a more or less. Dealers want ~$250 for one gear and if you have to replace one, you typically have to replace more. So, I don't see an HST being way more expensive to repair. Maybe a service tech can look up some prices and comment with data?
How long does a clutch last? Depends on what you do with it. If you are doing field work it's like a salesman's car on the highway. There might be a lot of miles or hours, but little wear on the clutch and brakes. If you are doing a lot of tight maneuvering, FEL work or moving heavy loads short distances the clutch may go out at 500-1000 hours. Maybe 1/2 that or 2x depending on the use and skill of the operator. FEL use drives you to feather the clutch to slowly power into a pile of dirt and the heavy load makes you feather it more to get going. Each time you use the clutch is scuffs off friction material. Slipping (feathering) the clutch does that for a longer time, heats it to a higher temperature and wears it faster. If field work is like highway miles, then FEL work with a gear transmission is like a taxi cab in crowded down town traffic. And yes, wet clutches last longer than dry due to heat dissipation to the fluid being much better.
When you look at the total lifetime costs, the higher initial purchase price and very slightly lower fuel economy is offset by the more frequent clutch replacements.
When people talk about "farmers" not using HST, they don't include that those tractors mostly don't have FEL's and they are probably exclusively used for field work. In those applications there is no benefit from HST, in fact the lower PTO hp and higher fuel use are a detriment. And when people talk about the benefits of HST, they don't mention that they have a FEL on it and may use it for applications like tight quarters mowing. They especially don't tell you that the typical operator has limited experience, so the ease of use provided by an HST pretty much outweighs all other factors. For example: the annual extra fuel cost is probably 10-20 bucks for an HST if 100 hours are put on and the fuel use is 5-10% higher.
Best advice is for you to try as many tractors as you can. FEL work, tight quarters operations, attach implements and anything else you can talk your sales person into letting you do. Then pick the one you LIKE the best.
Happy Hunting!
jb