Short answer: from about €100.000 for a basic medical device up to several million for an advanced medical device (about €500.000 for implants).
Long answer: that depends on several factors: the type of device, what data is already available for example if we can use already established validations (BAAT has several for you to use), which market(s) you want to get approval for, how much risk you are willing to take, what lead time until market approval you have in mind, experience in medical product development….
Generally you can say, that there are three major pillars that determine a project: Budget, Quality and Lead-time. Quality is mostly dictated by the Medical Regulations which means that you have 2 pillars left to play with. If you aim to shorten your lead-time to get market approval in the fastest way ever possible, the budget goes up.
What will this investment bring you and your customers?
And what will be the return on investment for you?