The company I work for, ThinkingSafe Ltd, provides online backup and recovery services for business data so please feel free to ignore the rest of this note.
Think of the purchase in terms of total cost of ownership, not just the hardware. So h'ware, s'ware, tapes (wkly,mthly,yrly versions), creating 2 copies a night (one stays local one offsite for D/R), management time and costs, plus courier costs to transport and store the tapes offsite.
Also to ensure you future proof your backups you need to take a strategic view that will commit you to DLT - S/DLT - whatever comes next or LTO - son of LTO, to ensure you have tape hardware and software around in 3,5 or 7 years that is compatible with archive data to fulfill your legal obligations.
I hope this was of use
Ed