So your saying that hosts generally don't have any room to expand the currently installed RAM? Or perhaps you are trying to say that hosts refuse to carry surplus RAM on their VPS servers? Maybe these servers are maxed out on RAM already? At any rate it's frustrating for me.
Xenforo uses Innodb, and with a large forum, RAM becomes one of the most important factors in forum performance, I can't seem to find a host that charges a reasonable amount for a VPS with what I consider to be a reasonable amount of RAM.
Because they have to markup the cost to make a profit and because the cost of adding more ram increases exponentially beyond like 16-32gb - they will want to get as many custs as possible on one box and RAM is the hardest thing to oversell as it's finite (compared to cpu and io)
RAM is not the only thing... but very popular by low-level admins theese days(don´t take it pers.)
the bottleneck is often the hardware as for ex. hdd, controller and so on.(as allways...you get what you pay for)
and the host has to calculate after the marked. as the marked will have low-price...you get low-price comp..
on vps and servers there is also a big potential in optimizing things like kernel, webserver and mysql.
and vps is not = vps...and is allways like a shared component.
a std.-install of a std.-distrubution is allways like a "one fits all" solution and optimizing is a very long task.
but often gives you a totally diff. server-feeling if it´s done once.
many users today don´t know that a small root-server with just 1GB ram in the right location has much bigger potential then a mid-size vps at a bad inviroment.
depending on wich country a small root-server kost not more then a vps and you have all recources to 100% all time.
A lot of VPS hosts also scale the CPU and disk allocation with the RAM being offered, which might explain why there is quite an increase from 1 to 2GB of RAM, because you will be getting other extra resources.
Most VPS providers (who don't oversell the RAM) take the total resources on the server and divide it up by the RAM.
For example, a server with 32GB of RAM might cost the provider $300/mo., if they aren't co-locating the server. To simply break even on the server, they would need to charge around $10/GB of RAM. At a minimum, you would be looking at $20 for 2GB of RAM.
So even if you don't need extra disk space, CPU, bandwidth, etc., you are still monopolizing the fixed amount of RAM. All the other "stuff" just comes with it, since the remaining resources are normally divided equally.