Costs & Time
If you order the Standard Parts according to the sources indicated there, you have to calculate with about 200 Euros including sales tax and shipping costs.
Special & Small Parts
The Special- & Small Parts will be about 150 Euros. Mainly because you either buy small quantities (always relatively expensive) or you buy larger quantities (which leaves you with lots of unused screws and other small parts). Maybe you can use them in future projects.
So the total cost of the alarm clock parts is about 350 Euros.
Depending on your experience and tooling, you have to expect about 30 to 50 hours as working time. Including the time for shopping research, ordering, preparation and soldering of display and control elements, working of housing and lower front panel, assembly of board, assembly of all parts, software installation, adaptation of constants, functional tests and wall mounting.