Why not send them an email or call or write a letter to them and ask why they don't have a sale or offer reduced shipping? If enough people contact them, it might work. Certain companies claim they have a sale during the summer but their sale prices are still overpriced..
Lazy S used to discount several % if you bought a full box. It was 16 plants, then last year it was only 9. But this year I don't see anything about that on their website, so I don't think they're doing that any more. I really liked what I got from them.
This year I've been ordering a lot from Bluestone. They send lots of discount coupons for specific types of plants with every order, and a 10% off everything coupon as well. I've been very happy with everything I've gotten from them, good packing, pots full of roots, healthy plants. I do remove the coir pots when I plant, though. I've just had too many problems with peat pots, don't really trust the 'bio-degradable' idea.
Bluestone also usually has an end of season sale (around May-ish?) where you can get things for a pretty big discount. I don't remember seeing any emails about the sale this year so I don't know if they haven't had it yet or if they're not doing it anymore.