Do the math! Industry averages are good for guidance, but your overhead is different from other shops, and like all business decisions, you need to make it rationally and based on your numbers. Just because you receive a check at the end of the month doesn't mean you're making any money. You may be surprised at how badly you're losing your shirt, or you might find that wire ins are a money maker for you.
If you don't already, keep track of all the ingredients in every arrangement you make and deliver, and ideally the time spent on each arrangement. At the end of the day (easier daily than at the end of the month), total up the COGS + labor + actual delivery fee for that arrangement, and if it exceeds 73% of the order's value, you have issues already, and you probably need to examine designer efficiency or product usage.
If you're under 73%, take the "we owe you" amount from the statement at the end of the month, and subtract the total COGS+labor+delivery for all orders for that WS. If this is negative, you have issues. At bare minimum, you should have enough to cover 30% of your shop's overhead (rent, utilities, insurance, social security contribution, etc), plus whatever fees are dedicated to that service (such as phone lines for the Merc interface).
If you're actually making money, recognize this is not a permanent decision. Every fee increase, payroll increase, tax increase, etc. needs to be factored back in.
It is very possible to increase profitability while decreasing income if you're cutting expenses by an even larger amount. Dumping TF may reduce your income by 10%, but may reduce your expenses by 15%.