I rarely buy plants anymore as I love to grow from seed. But this year I've been concentrating on planting up my front garden with perennials I have grown......and having been away for 2 weeks, I have lost a lot of seedlings and need to buy some bedding plants for a large planter outside my front door. I went to Homebase to purchase some petunias, I was scandalised by the cost of some of the flowers. Cosmos - 5 euro per plant! Primula vialii - 7 euro per plant! Both very easy to grow from seed. I had forgotten how expensive it can be to have a nice garden.....This is the exact reason I started to grow seeds.
Growing from seed can be quite intimidating, with far more failure than success. Particularly with some of the enticing challenging varieties available. Like rosemary, lavender, parsnips, etc. Not too easy for beginners, especially if all they have is a pot, bit of soil, and a windowsill.
I buy most my perennials in pots.. from the dead shelf if possible.. and let them seed around. I've done some from seed before, but my windows are usually filled with veg seedlings.. so never have space for them.