A quote from an earlier post of the originator. - "it is just for cleaning the odd domestic carpet and doesn't have to be an industrial cleaner".
Now we all know how good Nemesis Super & M Power is and 5 litres goes a long way and does a great job.
If it was manually agitated with a stiff carpet brush (thats cheap).
and then using something like a Neumatic George (again cheap) - I wonder what the result would be like?

to assist drying could even pick up a 2nd hand air mover for what - £100ish
Now thats cheap & within budget
and remember "it is just for cleaning the odd domestic carpet and doesn't have to be an industrial cleaner".