There is a solution for under $50 but the problem is there lots of DIY works and soldering to get it running. You'll need a CMOS camera ($5) + OSD module ($10) + 5.8ghz video transmitter ($10) + EasyCap USB module ($12) + 5.8ghz Video receiver ($15) and DIY antennas. Easy to buy bot lots of mods to make it works.