Instacart review: Inconsistent charges

Today, I ordered a large order of groceries from Food For Less to be delivered to my home, because I have a disability and am unable physically to do the shopping myself. The subtotal amount of the groceries alone per online Instacart receipt was $440.84. Once the tip, delivery, tax and service fees were added, that total jumped to $492.79. Upon reviewing my actual paper receipt from Food For Less (once my groceries were delivered) I learn my groceries plus sales tax totaled only $419.76 (a $24.96 difference when compared to what I was charged by Instacart for groceries + tax ($440.84 + 3.88) So basically, with fees and extra paid on the groceries, it cost me a whopping $73.03 over the actual cost of the groceries for this order. When I presented the issue to Instacart customer service reps, they just blamed it on Food For Less for inputting the wrong prices on their site. NO offer to reconcile the problem or refund me the difference. I just want to warn those who depend on this service to beware of these unethical business practices. Sad. : (