I can see several advantages to this:
1. Seeders will receive income. {The income can be used to buy bigger hard drives and faster data lines}
2. There will be less Leechers. {Once they need to pay for something, they would leech less}
3. Software developers can gain some extra income from this. {Those who depend on donations}
4. More people would start seeding and this will push the prices down.
So yea... it will contribute to a better torrent network.... The payment should only be linked to a validated seed.