Flourite will/can cost you anywhere between $15 - $25 a bag and you'd need a minimum of 5 bags, maybe 6, IMO for a nice substrate banked back to front.
There is a product called 'Turface' or 'Schultz Aquatic Soil' that is very, very similar to Flourite....a bit lighter, but far less expensive and again, IMO worth the savings if you are financially challenged.
The difference in weight means it's a bit more difficult to plant in because it doesn't hold them in place as well, and gravel vacing is a bit trickier. The good news is that it is loaded with nooks and crannies (CEC) which enables it to give housing to good bacteria that are very beneficial to the tank's environment. Over time these nooks and crannies fill up which makes the substrate heavier and easier to work in.
I use both Flourite and Schultz and, in a big tank would either mix the two or go with the Schultz alone if finances dictate that route. I'm happy with both.
If I remember correctly Schultz was going for about $15 a bag which was approx. 40lbs. in weight. This would run you about $30 for your tank, a considerable savings.
Len