I agree with smartbookings, the competition is very strong when it comes to selling beauty products online, and to top it off I know from 15years experience its not as easy to get a store to the top as it is a normal web site.
You asked if its more trouble than its worth, just like any other business it comes with its own problems.
Set up Costs
This is difficult to answer, there are a few ways you could work this, and yes it could be very expensive, the set up costs can be kept to a minimum its getting the shop where it needs to be to make the money.
For any online store you need to be (people say upto page 8 of google i disagree slightly as most people have found what they are looking for before page 8) no lower than page 4. For you to get a store selling beauty products online you will need to employ a very good seo company. The costs would be between £100-£300pm. And a word of warning with selling products online do not expect overnight success I would guesstimate that it would take a good 3-6mths for you to even rank into the top 4 pages. Again this depends on what your selling and the seo company you are using. Oh if you do ring around any seo company and they say they work close with google, put the phone down and try someone who isnt going to lie to you to get your business. Also get information from them about success stories they have been involved in, for example it would be easy to get you to the top of google if someone wrote "beauty products by serenity in bedford". the hard part is to get you to the top if you write "beauty products".
With online stores you are already on a back foot if you cant come close to their prices, I would suggest loss leaders, or other ways that may cost you money for the customer to buy from you. But dont give up just because they are cheaper than you.
What I would suggest is to set up an ebay account with a link from youir site, and gradually build it up and see if there is a market out their for the products you intend to sell. If not it hasnt cost you an arm and a leg trying.