810 has a viscosity of 28-30 @ 20°C , pretty similar to usp grade mct oil . Mig840 has a viscosity of 9 @ 20°C , so actually alot thinner than 810 . Hard to tell just by shaking the vial or something , but you'll notice a huge difference in how fast 840 will filter or even push through a smaller guage needle...
One of the big reasons its such a good carrier isnt just its ability to hold higher concentration brews or its viscosity which is usually what people talk about . But its biggest advantages imo is it's a much healthier oil compared to other food product carrier oils because it oxidizes at a faction of the rate of most other oils . It also has a absurdly high thermal stability which is great for making things like injectable winny or base compounds that need to be worked at higher heat , which can break down and ruin the stability of lesser oils .
The cost really isnt bad though , a liter is 50 bucks which for the average homebrewer will last forever basically, and if you have a lab you can buy it wholesale for like 18$/liter , so pretty much on par with other oils ... I think its definitely worth a little extra money , but I also dont get pip from anything so i might be a little bias . I could inject motor oil with turkey baster and probably not get pip lol ..