Not all salon treatments are the same. How good the treatment is depends on the quality of the machine and how experienced the therapist is. The IPL machines that you can buy are not as good as salon treatment - we get clients who have abandoned theirs in favour of treatment with us.
In my salon we have a £20,000 machine (that we service regularly and replace every 2-3 years) and 13 years experience. There is no comparison.
A decent salon will do a free consultation (you might have to pay for a patch test) Ask them how well your hair is likely to respond to IPL, if they explain that your hair will be tricky to treat, you probably won't find a home use machine any good.
You could try having just one treatment (don't get suckered into paying for a course) and see what difference it makes. You should have a noticeable reduction in regrowth, if not, don't go back.
After 3-4 treatments you might have 50% less hair and all the hair should be finer and less noticeable and you might be perfectly happy with that. There is a point where the hair that remains is difficult to treat, you get diminishing returns, so if you want a perfectly hair free result you will need lots of treatments. This is where the grade of machine makes a difference - it's the last bit of hair that's the hardest to treat.
I guess that the best financial option would be to get 50% of the hair removed by salon treatments, followed by home use machines to get rid of the next 25%, followed by salon treatment for the last bit - so you'd be replacing say three salon treatments with maybe a year of home use. But to be honest, everyone's hair is so different that what would work well for one person would be no good for another.
Either way, stay away from groupon offers. You'll only get inexperienced salons and newly qualified therapists, practicing on the "deal" customers. You can be scarred with a salon machine used inexpertly without proper supervision so don't take a risk.