I've never bought buckwheat for Merit seed before but I see they have buckwheat for sale at a decent price but they'll probably get you on the shipping. Hancock has it for more per pound but no shipping.
At Merit Seed, we combine tradition with innovation to supply Ohio’s farmers with the finest seeds. Committed to quality, community, and agricultural growth.
Most online sites I've checked are showing $25-$35 shipping. If I was you I would check around and see if there's any co-ops that would be a reasonable drive.
Don't know how the coops work in your area, but here, the manager can order any seed I want in 50 lb bags. Sometimes I can find a better price online, but often, with shipping cost added I just buy from teh coop. When I do order seed on-line, I've use Welter Seed & Honey most often. I've been happy with them.