No doctor can legally sell any medicine/gel. About the pricing for treatment, I can't comment, because the treatment might be deep scaling with flap surgery,which sometimes requires more than 3 sittings and cost is much higher than simple dental scaling (supra gingival scaling).
Next Steps
You can always have a option for a second opinion. But if you have moderate to severe periodontitis (gum problem) then treatment plan will be almost same.
Health Tips
It's better if u go to your same doctor and understand the exact reason for gum bleeding and the possible treatment options for that, will finish your all doubts.