Prfit centers seed/fert. vs. mulch

[montlandscape]

Hello.
For anyone out there that sells both bulk landscape materials and lawn fertilizer/grass seed, which line has a larger margin? I've been a landscape contractor for twenty years and am going to expand into one or both of these areas. I know the market very well for bulk landscape materials but am not sure of the % increase (mark up) for seed/fertilizer. We are located outside Philadelphia, PA. Thanks for any info. in advance.