If it were my decision, I would offer three editions:
1) A free decompressor, that can also do a *few* compression algorithms (like zip).
2) A Regular version, that has most features in the package (all algorithms) but no support. Sells for maybe $1-$3. Average users would use this.
3) A Pro version, that has every feature possible (like batch capability, etc) and includes support. Sells for around $20. High-end users would use this.
I have said for a long time that sales are inversely proportionate to cost, if interest already exists. There is obviously a market for specialized compression software, and it is large enough to support continued development. But if you price your software too high, you drive people to the free software and away from yours.
1,000 copies at $20 is $20,000. But 50,000 copies at $2 is $100,000. Plus you have 49,000 MORE users talking about your software, recommending it to others.