This page is includes information on the costs of different plastics used in mechanical engineering.  The costs are obtained by reference to links found on the internet (links 1,2 below).   I have converted the costs to english units although the costs are based on american costs in dollars and imperial units.  The costs are really only useful in as relative indicators. Real costs depend on country of supply and market conditions.

The resin prices do not seem to relate directly to the cost of standard products e.g Tube, rod etc

In order to try to arrive a reasonably practical costs for plastic components I have obtained the cost of a representative plastic stock (a rod 50mm dia x 0.3m long).   This stock has an approximate volume of 0,0006m³.   This size has been selected because the stockist which are conveniently accessible on the internet, generally provide costs in dollars /foot length with diameters in inches and the above size approximates to 2" dia x 1 foot long. I have calculated the volume and weight and used these results together with the raw material prices above to obtain the theoretical basic material costs.    These have been tabled below against the prices obtain from the internet (link 3 below) for rod prices.