Use a spreadsheet to grow the discount of your hourly rates as the block sizes increase. Analyse mine. Encourage the purchase of larger blocks with larger savings per hour for your client and larger upfront checks for you. Build a range of what is acceptable to you from highest to lowest then spread them proportionally to the block size and manually round off the numbers to make them easy for humans to process.
À la carte hourly rate is your typical billable invoice rate plus an incremental premium. Set this higher to allow for, yet discourage, purchase of only one hour at a time for small projects or to allow them to buy enough time to finish off a project without buying time they don't want or need.
Yes these rates are very low. Make a different set and quote different block sizes for each type of job/skill/service.
