A new long block VQ40DE from Nissan is around $7000, not including tax, labor, fluids, filter, intake gaskets, etc. So, that question is answered!
The upper chain problem doesn't occur because the plastic tensioner faces weren't made good enough, as they aren't much different than the ones used in other VQ engines that have been around since 1995 in the US. The problem was caused by poor quality control of the upper timing chains, which were made by Borg-Warner. What happened is that the tooling would wear that stamped out the link plates of the upper timing chains. As that tooling started to wear, it would stamp out chain links with sharp edges; the more wear on the tooling, the sharper the edges. These sharp edges on the links would cut through the plastic faces and the fact that there are different levels of wear on the tooling depending on how many links it stamped out is why some VQ40DE engines have no chain problems, some don't have them long after 100,000 miles and some can have them as early as 25,000 miles. If the upper chain links were properly manufactured from Borg-Warner, likely non of the VQ40DE's would have timing chain issues. The current replacement upper chains you get from Nissan will not have this problem. So, the idea that you are going to get better parts on the aftermarket than the ones you can get from Nissan probably isn't true.
Now, the gears really don't wear much and should not be in need of changing. The primary chain will also probably be fine and is not recommended for the repair by Nissan, although, I usually change them because it is easier to identify the colored links on the new chain which line up to the timing marks. Most of the time, even the plastic guides with a lot of mileage on them often don't show any wear on them unless the tensioner faces were worn down to nothing. One thing you should know that in order to replace the whole, upper tensioners, you have to remove the rear timing cover. There is usually nothing wrong with the tensioners other than the plastic tensioner face which is all that Nissan replaces during the repair. The Nissan TSB on the repair lists all of the parts for the repair, which is basically the upper chains, two tensioner faces, a number of cover seals and a front crank seal, coolant, oil and filter and RTV sealant (personally, I would skip what Nissan recommends and get a caulk tube of Permatex Ultra Gray Rigid High-torque RTV sealant; you'll be laying down a lot of sealant on the front cover and using a caulk gun is the easiest way to do it!). I think the warranty labor time is 6.0 hours, IIRC. Now, this is using what has been coming a hard to find ring gear tool, which you will need if you want to torque the cam gear bolts without removing the upper intake plenum/timing actuators/valve covers. If you don't have the tools, you will need to R&R those parts so you can use a wrench on the flats of the cams to hold them in place. The ring gear tools allows one to torque those bolts using the timing chain to hold the gears and keep the cam from turning. It also makes it easier to remove and torque the crank pulley bolt if you don't have an air impact gun.
The typical repair cost in an independent shop is $1200-$1600, parts & labor, depending on the shop's rates and whether Nissan or aftermarket parts are used. However, that price can get higher depending on the "add-ons." The "add-ons" are parts that some people will want to replace while in there, such as the primary timing chain, guides, primary chain tensioner, thermostat and water pump. I would replace the water pump if it's original and has high miles on it; it's just so much easier to replace at this point. This all said, the $4100 quote from the dealer is absolutely ridiculous! You could print off the TSB and ask them how they came up with a labor rate amount that is three times higher than what the Nissan warranty time is for the job (most labor guide, retail hourly rates are usually around 1.4 times the warranty labor time). As far as the Cloyes kit, it should be fine, it's just that it's overkill in my opinion and you'll have to make the decision of just using the tensioner faces off of the tensioners (and try not to damage them trying to remove them) or install the whole tensioner and add a whole lot more work in removing the rear timing cover...or, just buy a set of tensioner faces to use and not use the tensioners in the Cloyes kit. Decisions, decisions!!