Right now on Staples you can get 500 Standard Business envelopes for $3 and they ship for free. These are regularly $8.49. You can buy up to two of these.
Product Description:
Standard grade envelopes.
#10 (4-1/8″ x 9-1/2″)
Gummed closure with V-flap
Perfect for everyday mailings
24 lb. white wove paper
Staples Brand 100% Satisfaction Guaranteed