I think you will find that everyone has there favourite I use Seachem prime which I changed to from Tetra aqua safe as it is more concentrated than the aqua safe, so I use less so it costs less

.
Some people when doing around a 25 to 30% water change do not use any, I think

I understand the reasoning behind this practice but personally I do not feel happy doing it at the moment so dose as recommended with a dechlorinate maybe one day I will evolve to this pratice? But hey everyone is entitled to do what they feel is the best for there fish
Others use pond dechlorinate as it is extremely concentrated and gives you very good value for money, there are lots of posts on these practises on here you just need to do a search for them.
An interesting article on dechlorinate brands: http

/www.thetropicaltank.co.uk/rev-cond.htm
Of course the other way of cutting costs is to find the most competitive price for your favourite brand which is almost always found on line with a little investigation, I have found buying the larger containers is cheaper and I personally always buy when I am ordering other bits and peace's like food and hardware to save on postage as some places offer free P&P with orders over a certain price.
I hope this helps a bit regards onebto.