There is some cheaper options for a PL Encoder module on eBay, and a few other companies sell some as well. If you just need the basic encode then no problem, that can be done for $20-$40 and a little work installing it. If you wanted full encode/decode than thats different and a bit more involved installation wise but still do-able.
Tell me one thing though, what is the make and model of the radio that your thinking of getting?? Would help in giving you more accurate advice.
You can get a brand new Yaesu FT-2800M, 60W and full encode and decode, for about $120.