Please be very careful when it comes to plastic materials and their terminology.
Acetal is the industry standard, generic term for Polyoxymethlyene (POM). POM can be catagorised in to Homopolymer and Copolymer Acetal.
Delrin is the trade name of a Homopolymer Acetal produced by Du-Pont. This is not the only type in the world. Homopolymer Acetal is also produced by Asahi under the trade name Tenac.
In addition there are many producers of Copolymer Acetal in the world including BASF (Ultraform), Ticona (Hostaform), ZAT (Tarnoform), KEP (Kepital), MEP (Iupital), LG (Lucel).
In general terms
Homopolymer materials exhibit higher mechanical strength and higher heat resistance.
Copolymer material exhibit greater dimensional stability, superior creep resistance at high temperatures, increased hydrolysis resistance and greater chemical resistance.
It may well be that Delrin commands higher prices than other materials but it is not true that other Acetal in general are in any way inferior. Your choice of material should depend on the application it is being used in.