Well firstly, soap is a wash off product. We are basically waterproof anyway and the whole function of the soap is that it will latch onto the dirt and oil on our bodies and whip it away down the drain.
Secondly, the soap making process is very harsh. We are using Sodium Hydroxide and quite high temperatures - over which we may not have any control... especially if your soap gels in the mould. If the essential oil does not burn off during the initial soap making process (and this is why we use such large quantities in soap making - sometimes up to 3% of the base oils), the final smell is not always quite what you expected. It has been altered by the process. If it is going to have any therapy value it will be in the smell - but I can't be sure that it is what an aromatherapist would expect.
So for soap making I always choose cheaper essential oils. This does not mean that my soap is a lesser product. It's a question of raw ingredients fit for purpose rather than of quality. Similarly if I am making a night cream for my mother-in-law I will always use an organic essential oil from a reputable supplier.
And this brings me to the essential oils suppliers. It is very easy for us to be fobbed off by poor quality oils sold at premium prices and not to know the difference. How would we know the difference? I have known aromatherapists rave about a particular oil until they smelled the same oil from another supplier... and even then... plants are natural things... what they do one year, they don't the next.
Each batch of oil will be subtly different from the last. And the difference between lavender from different suppliers can be astounding! You need to find an essential oil supplier whom you trust and be guided by his/her advice as to purchasing the correct product... i.e. tell them that you are making soap, or that you are wanting to use it in a massage bar and they will be better placed to advise you which grade of oil to buy. Hint If you are unsure, order a very small quantity, the smallest you can and then be guided by your nose, if you like it... ask for a bigger quantity from the same batch.
ABOVE ALL, BE GUIDED BY YOUR NOSE!
This is very important.YOU must be the judge. Your nose must be the one to say if it is good or not. Don't worry if you think you have a poor sense of smell. The more you use your nose to smell different things the better it gets at smelling. Do not be tempted to use more than the recommended amount in your product. And be aware that some oils have side effects (e.g. making your skin more susceptible to sunburn) and these should be taken into consideration. But most of all... do lots of sniffing and have fun.